Tags: accountability, Alberta Education, assessment, diploma exams, post-secondary, teachers
Recently, many people have been writing my office with concerns about the diploma exams that were written at the end of January 2010. I asked the department to thoroughly investigate each of the issues that were raised.
The diploma exam program in its present form is a significant milestone in students' formal education. These tests are designed to be exit exams that assess students' knowledge of the Alberta programs of study. Like the courses themselves, they expect a high standard of learning from students. They also ensure every student is assessed using a common standard across the province, and thus provide a highly reliable basis for admissions and scholarship decisions made by post-secondary institutions across the country.
How diploma exams are developed
All diploma exams undergo a complex, quality-controlled development process which takes about 18 months to complete. These development processes ensure that each examination covers as much of the curriculum as possible in a pencil-and-paper test, and that each question is fair and appropriate for Grade 12 students in each course. During development, experienced classroom teachers with a thorough knowledge of the program of studies are extensively involved in the creation of test blueprints, item development, field testing and validation of every exam. About $10.5 million is spent on diploma exams each year (another $4 million is spent on provincial achievements tests; by contrast, about $30 million is spent to develop curriculum).
While diploma exams are designed to be at a consistent standard of difficulty each year, it is not possible to design an exam that is exactly as difficult as another exam. Therefore, diploma exams are equated: by reusing some exam questions, it is possible to adjust students' marks to compensate for variations in difficulty. This ensures that only student knowledge is being tested. You can learn more about equating here.
Differences between teacher-awarded and exam marks
The most common concern that has been raised is that diploma marks are significantly less than teacher-awarded marks. This is not unusual. Diploma exams are designed to have an average of 65 per cent (the mid-point between the acceptable standard of 50 per cent and the standard of excellence of 80 per cent). Designing the test to a 65 per cent mean does not preclude the number of students attaining either standard from increasing; it merely ensures the accuracy of the test as a tool for identifying attainment of standards. Should the number of students attaining the standards increase, the average achieved on the test provincially will increase above 65 per cent. Each exam in January 2010 was at approximately the 65 per cent level (see the table below).
| Course | Average teacher-awarded mark (per cent) | Average diploma exam mark (per cent) |
| Courses used for post-secondary admissions | ||
| English Language Arts 30-1 | 72 | 62 |
| Social Studies 30-1 | 73 | 63 |
| Pure Mathematics 30 | 73 | 69 |
| Biology 30 | 73 | 66 |
| Chemistry 30 | 73 | 66 |
| Physics 30 | 75 | 62 |
| Français 30 | 77 | 67 |
| French Language Arts 30 | 79 | 66 |
| Courses not used for post-secondary admissions | ||
| English Language Arts 30-2 | 64 | 65 |
| Social Studies 30-2 | 65 | 65 |
| Applied Mathematics 30 | 66 | 62 |
| Science 30 | 70 | 66 |
Teachers' classroom assessments of students have not changed over time, with averages that have hovered around 75 per cent provincially and a relative distribution that has remained constant. Exam marks have also been consistent over time, at about 65 per cent, with a similarly constant distribution.
It is not unusual for exam marks to be lower or higher than teacher marks because of differences in assessment standards and practices. Indeed, it is noteworthy that there is much less difference between teacher-awarded marks and diploma exams marks in courses that are not used for post-secondary admissions. Addressing these discrepancies is one area where we need to do a better job, and we are involved in discussions with the ATA, ASBA and deans of education about how to do this.
Individual cases where the diploma and teacher-awarded mark vary greatly are not generally investigated, unless exam cheating is suspected. If a student's mark drops significantly on the diploma compared to in class, the first check is in the classroom. For instance, students who had high marks going into the exam may be overconfident, and not study enough prior to the test. However, if there is a noticeable difference between the diploma mark and the teacher-awarded mark for a large group of students throughout Alberta, this is explored.
To ensure that students' marks on diploma exams are fair, marking of exams is based on a standard set of scoring guidelines that are available to teachers and students throughout the year. Every examination is marked anonymously by two independent markers, and the marks they assign are blended together to determine the final score. If the two marks differ significantly, the paper is read by a third marker, and the resulting score is assigned. In rare instances where the third reader's score is significantly different from those of both previous markers, the paper is set aside for a fourth read. Although this is a rare situation, it illustrates the extent to which steps are in place to ensure students receive a fair evaluation. These marking processes ensure that the examination measures a student's achievement as objectively and accurately as possible.
In short, a student's mark being lower on the diploma exam does not mean that the exam is flawed any more than a student's mark being higher on the exam means the teaching is flawed.
The difficulty of exams
Another concern that has been raised is that exam marks dropped in January 2010 because of the difficulty of new programs of study. This concern has been raised about three programs of study: English Language Arts 30-1, Physics 30 and Social Studies 30.
In the case of English Language Arts 30-1, the program is not new. However, diploma exams in English Language Arts have shown a serious decline in writing skills (Part A of the exam) over the past five years. Alberta Education staff has investigated this decline with the assistance of experienced classroom teachers, and have found that exam difficulty has not increased over the past five years in a manner that would account for the continual decline in student scores. In other words, the decline in scores is a reflection of a decline in student abilities that we are now working to address.
The current Physics 30 program of studies has been in use since September 2008. This new program of studies focuses on students' conceptual understanding of physics, emphasizing students' grasp of the "why" behind the things they do. In the old program, students with strong calculator skills could achieve honours marks with little understanding of physics. In the new program, these same students would struggle because they need to explain why they used a specific calculation to solve a problem.
The first diploma exam to test the new Physics 30 program of studies was administered in January 2009. Because student marks on this exam were low, these marks were scaled for a province-wide average of 63.7 per cent (in comparison, the provincial average in January 2008 when the old program of studies was assessed was 68.1 per cent). As can be seen in the table above, the diploma exam marks in January 2010 averaged 62 per cent province-wide, close enough to the intended average of 65 per cent that scaling was not necessary. Teacher-awarded marks have been consistent throughout the introduction of the new program of studies: the average Physics 30 school-awarded mark in January 2008 was 74.4 per cent. In January 2009, it was 74.2 per cent, and in January 2010 it was 75 per cent.
The current Social Studies 30-1 program of studies was introduced in September 2009. Over the three semesters prior to the province-wide introduction of this program, prototype versions of the new exam were field-tested in numerous classes around the province to "fine-tune" the written response assignment and the scoring rubric. Before the exam, a diploma bulletin with sample writing assignments, scoring rubrics and exemplars of student responses was made available to teachers and students.
January 2010 was the first administration of the diploma exams for the new Social Studies program of studies. Overall, the transition to the new examinations has been successful, with marks close to the intended provincial mean of 65 per cent.
It is true that Alberta's diploma exams are generally more difficult than comparable exams in other provinces, or indeed, elsewhere in the world. This is a good thing! The Alberta programs of study have wide respect because they are challenging but by no means impossible. Leading universities like McGill have publicly acknowledged that Alberta students' marks indicate a higher level of achievement than elsewhere, and that this positively influences their admissions decisions.
Removing written response from math and science exams
Last fall, I made the controversial decision to remove the written response portion of the math and science diploma exams. As was expected when this decision was made, the removal of this component has not affected student marks.
While many people assume that students performed better on the written response component of the mathematics and science diplomas, this is not the case. For example, the provincial averages for the past 15 administrations of Biology 30 show that in 12 of the past 15 administrations, the average on the written response was lower than the machine-scored portion, while in Pure Math 30, 11 of the past 15 administrations have had a lower average on the written response portion than the machine-scored portion.
French Language Arts 30 and Biology 30
In response to concerns about the timing of diploma exams in January and June 2010, the diploma exam schedule was adjusted so that most students would write only one exam per day. However, French Language Arts 30 and Biology 30 were scheduled on the same day, as relatively few students wrote both these exams. Education staff analyzed the diploma results from January 2010 and found that the results of the 181 students who wrote both exams were comparable to the results of students who wrote only one exam that day.
High Stakes Testing and the Weighting of Exams
I am well aware of suggestions that Alberta's testing programs are "high stakes tests" that place undue stress on students. In the case of Grade 3, 6 and 9 Provincial Achievement Tests, these assertions are simply untrue. Those tests do not drive curriculum (as with the diploma exams, assessments are constructed after the curriculum has been prepared), and they have no impact on students' progress or teachers' pay or promotion. They exist solely to provide to teachers, parents, principals, superintendents and Alberta Education information that can be used to formulate improvement strategies.
It is a matter of concern if, as a result of outcomes on achievement tests or diploma exams, superintendents put pressure on principals who then pressure teachers to improve test results by inappropriate means. There is, however, nothing wrong with a superintendent or principal recognizing jurisdiction or school-wide problems and endeavouring to effect strategies or supports which address the problem. I am very interested in hearing from teachers and principals who have been pressured to improve test results by inappropriate means, but while I have heard a lot of second hand stories, no one has yet come forward to describe a personal experience of this nature. (Please contact me if this has happened to you!)
In the case of Grade 12 diploma exams, these tests are high stakes for students, as they are exit exams which form half of a student's final grade, can be the deciding factor in whether or not a student passes a course or achieves a high school diploma, and have a significant impact on post-secondary admissions and scholarship awards.
However, I have yet to be convinced that any of these functions is inappropriate for a diploma exam. It is entirely appropriate to check that students have learned what they are expected to learn over the course of their time in school. In passing a class or receiving a diploma, I have to question whether a student has really fulfilled our expectations of him or her if the diploma exam is what makes the difference between success and failure — a final mark of 51 per cent is not all that different from a final mark of 49 per cent. The point of education is to truly understand, not achieve the bare minimum to step over a statistical hurdle. And student success in high school — both in class work and on the diploma exam — prepares students for challenges to come in post-secondary programs which involve much more difficult and time-restrained final exams.
To me, it is an open question whether diploma exams should be given the same weight as teachers' marks in determining students' final marks. Many people have suggested otherwise, variously pointing to 60, 70 or even 80 per cent as the appropriate teacher-assigned fraction of a student's final mark. In my view, adjusting the weighting necessitates having the assurance that teachers are marking students on a common, consistent basis.
Teachers and assessment
Ultimately, discussion about diploma exams and teacher-awarded marks comes down to two issues: whether diploma exams are an appropriate assessment of all the attitudes, skills and knowledge that students are expected to learn; and whether teachers' assessment of the same is consistent across the province. I believe we need to improve on both counts.
While Alberta's diploma exams are built to be a complete assessment of the content in our programs of study, there are skills and attitudes which cannot be effectively measured by a pencil and paper test. As we look at the next steps arising from Inspiring Education, we will be moving to a competency-based system that also emphasizes other student abilities, like thinking creatively and critically, building relationships and being resilient. There will still be a place for pencil and paper tests like our current diplomas, but our assessment programs will likely be much different from those of today.
As a matter of fairness to students, it is essential that teachers across the province assess their students to a common standard. We do not need standardized assessment if we have standards of assessment, and unfortunately, I do not believe we presently have standards of assessment of a sufficiently high caliber that are widely understood by teachers, principals and the general public. There can be a great deal of variation in the curricular expectations of different schools and the assessment practices of teachers, which is not fair to students.
Diploma examinations are of great benefit to teachers in implementing a new curriculum because reviewing detailed results can identify areas where improvements to instructional programs are needed; however, it generally takes a few years for teachers to adjust to a new program. Regrettably, the ATA does not permit staff from Alberta Education's Learner Assessment sector to speak with teachers at specialist councils and conventions on matters related to the tests, depriving teachers of a valuable professional development opportunity.
As I noted above, we are working with the ATA, ASBA and deans of education to ensure that new and continuing teachers develop the skills they need to fairly assess our students. Until we have these standards of assessment, diploma exams are a consistent common assessment that is marked to a common, unbiased standard.
We have already had several fruitful discussions about the future of assessment, and will no doubt be having many more in the coming months. It is crucial that we get assessment right — our students deserve no less. As always, I welcome your input.
Comments
I can see Diplomas being worth perhaps 30% of a student's final grade. The 50% seems a bit excessive, especially when a student has worked very hard all semester to achieve good grades and then to have half their final mark determined by one two hour exam. Even in University the final exam is usually not worth more than 40% of your final grade. It just seems to me that the teacher's assessment of a student should carry more weight than a one-time, often stressful, exam.
The table of diploma results you show says that Science 30 is not used for post-secondary acceptance. I am a nursing student at Grant MacEwan and my Science 30 course was used for post-secondary acceptance into my program. Are you saying that Science 30 is no longer going to be accepted for post-secondary programs?
Sam Crawford
Dear Minister Hancock,
Thanks for this communication. I think it's great that you are posting these blogs.
With respect to standardized tests, there are (at least) two important issues that I would like to see addressed. The first is the way(s) in which achievement results are used by some schools, parents, and organizations to "market" a school as superior. Often such tactics rely on simplistic understandings of what the statistics mean. Further, achievement exam scores eclipse other aspects of the important work that schools do. Schools working hard to meet the needs of lower SES students or high numbers of recent immigrants may be branded "bad" schools because achievement scores are not as high as schools serving higher SES families.
The second issue I'd really like to see you address is how standardized exams, along with a packed curriculum, leave teachers and students with so little time to engage deeply with the curriculum, or explore those wonderful, serendipitous "teachable moments" that offer significant learning opportunities. There's nothing worse, as a teacher, than saying, "we have to stop learning now, kids, because we have to get back to the curriculum."
I don't disagree that schools should be accountable for a standard curriculum, and for providing all kids with quality learning experiences. But are standardized tests really the only way we can do this? And could we at least acknowledge that while standardized testing addresses some problems, it also creates new ones?
Thanks very much,
Laura Servage
Doctoral Student, Educational Policy Studies
University of Alberta
The Alberta Teachers Association has provided a response to the Minister's blog post which can be found on the Real Learning First blog.
I have decided to go into the school of business. I just need my math 30. I am now going to night school for my second and last semester there. My first semester my mid-term was 92% and my final was 86%. I did so well on my final and all term long that it wouldn't have mattered much if my final were worth 50% or 30% of my grade.
But where it does matter is now in my math 30 course. As I will be doing my diploma exam as a prerequisite into SAIT. This semester I have been faced with an obstacle that I would have never saw coming. An obstacle that could very well re-direct my future and in a negative way.
I have wide respect for teachers as their jobs are hard, the pay isn't what is should be and teachers do put up with a lot of immature students as well as impossible students I am sure. But my fury, is how one teacher has complete control over a students course term testing and marking. I feel that I have been treated very unfairly and I have no control to make any changes.
My teacher has made up her own tests that are NOT based on my math book or math workbook. I don’t know where she is getting her material from. It has made it so much harder for me to get by this term. I just don’t think its very fair. She has admitted that she wants her students to push beyond their parameters. My only thought to that was, "We should be studying the book material that was given to us and not going way beyond that material."
At this point, I am starting to believe that maybe a standard curriculum would be more suffice. At least I would be confident that my teacher is NOT setting me up for failure. I am THANKFUL today that my final diploma mark will be 50% of my term final grade. If it weren't, I would certainly fail and not be able to get into SAIT. The fact that the diploma is not 100% written by my teacher gives me hope that I still might pass and start living my dream out loud.
I am a grade 12 student, and I have achieved good grades my whole life. All of jr. high, as well as my high school years my average has been over 80% .. up until grade 12 that is. So Minister of Education, are you telling me that my teachers have been lying to me my whole educational career? Are they just liars, and I am actually stupid because one TWO HOUR TEST determined that for me? My whole life I have been reinforced I have been a good student, while this one test told me I was not. Something does not match up here. I do not understand how I can go in with a 90% and finish with a 70%. Yes, I know the "stats" may not align with my experience- BUT I DO NOT WANT TO BE JUST A STATISTIC. I am an individual with dreams. I worked my butt off my senior year, and I didn't play basketball this year either. Want to know why? It was because I was being devoted to my STUDIES. I knew what was at stake in January with these exams. I have been playing competitive basketball since jr. high and in grade 12 I would have liked to return to my senior team. I was trying to be responsible for my future, so instead of basketball I devoted my time to PAID tutors for extra study sessions and PAID diploma prep classes, in order to insure success on these ridiculous exams. I feel like I should've just played basketball and I should have just saved my money from the tutors because my diploma marks showed absolutely nothing for my preparation. Nothing. So- thank you Alberta government, for absolutely diminishing my confidence. Thank you for wasting my money. Thank you for ripping away my 85% average. Thank you for taking away thousands of dollars in scholarships. Thank you for taking away University acceptances. Thank you for putting my future on the lines of a two hours test that is strictly multiple choice- in which some students struggle with. Thank you for shooting for a 65% average on your stupid tests. Let me ask you this: why would you set your students up for failure? You yourself proved that classroom marks are always higher than diploma scores. It's like you want our grades to go down. So thanks for that too I guess. I was accepted into 5 universities, I put in hours and hours of time studying for exams. It is not like I am someone who doesn't care about my education- BECAUSE I DO. Also- about the Math 30 Pure exam. Is it not true that the so called "secure" test got leaked, and that people had access to this? Is it not true students were caught CHEATING on this exam? If a few kids got access to this, who is not to say there were thousands more, just no one knew it? How is it fair those Math 30 exam marks were being counted into our marks when the exam was not even secured!!!! Once again, not fair. Also I have talked to social teachers from different schools, and different school divisions and EACH ONE OF THEM SAID their averages were significantly lower than any other year. The teachers from my school said it was one of the hardest exams they've seen in a long time. How are students suppose to adapt to this. The other thing is it seems the only students who appreciate these exams are the kids who DEPEND ON THEM to pass. It is easy for a kid to walk into a multiple choice test, score a 50%, and pass the course. It seems Alberta Education is just reinforcing the kids who don't put any effort into their studies. While, someone like myself, going in with an 86%, worked hard all year and devoted hard work into that mark just get a slap in the face. It is NOT likely for a student to score an 86% on a diploma, so I went into the diploma with a feeling of automatic failure because I almost knew my mark was going to drop. It also seems Mr. Hancock is somewhat blaming teachers for declining diploma scores- but this is completely not fair. Teachers absolutely HAVE to "teach to the test." How can they not? THAT TEST is worth the WHOLE semester that the teachers have been teaching us! It is NOT the teachers fault for a flaw in Alberta Education.
I, being a grade twelve student, feel that the diploma exam counts for too much of a student's final grade. All year students work extremely hard and write multiple tests but then one exam determines fifty percent of your grade! Especially this year with the leak of the Pure Math 30 exam, I have come to feel that hard work is not rewarded. A student who works endlessly may get a bad mark just because they had ONE bad test. Another student simply has a good day and ends up with a good mark. We should try to create a system that will allow us to trust(with great confidence)that teachers will not inappropriately increase students' course marks.
Minister Hancock,
I agree that your communication here is welcomed and is important. As a Social 30 and 30-2 teacher as well as English 30 and 30-2, I do tend to 'hear' the students who resent the 50% weighting of the diploma exam. It is a shame that a year's worth of study and assignments should only count for half a student's mark. This is creating problems for teachers and for students. One difficulty for teachers is that if you know your hard-working, intelligent students are most likely going to receive an average of 10% less on their diploma exam, you MAY want to inflate their mark slightly to offset this almost guaranteed discrepancy. Just a thought, one which I am sure you have considered.
And so, though I agree that there must be standards and that the bar should be high (as we humans generally only jump as high as we need too), in the real world our system appears to be failing students and is rather demoralizing for teachers.
P.Graham
I think it is beneficiary for the goverment if people are uneducated. The less people know the more goverment could get them under control. In this case spending 30 million each year out of tax payers money and making diploma exam worth 50%(so everybody is guaranted to fail, and no one have access to university) make so much sense. Alberta provincial goverment will do anythink to keep student from getting into university so they get smarter. APG out their know a smart citizens is also dangerous to the govermet citizens. So keep making diploma exam more difficult and spend more money on diploma exam( instead of putting those money toward scolarships) and you are guaranted to have better future for this province!
I'm a grade 12 student, and I think that the 50% threshold is fine. Compared to the work expected of us in class, the diploma exams have so far addressed straightforward knowledge and concepts which anyone who has been paying attention in class and studying should be able to comprehend. The standard of excellence is quite achievable, and I'm a little disappointed that so many Albertan students find themselves unable to achieve this reasonable standard. (For a standard that is much more contentious and difficult, look at the IB's curriculum).
I think that the weighting of a diploma exam so high is necessary to ensure that our students are competent when they proceed into the world of work and/or post-secondary education. This assessment helps implement a system of checks and balances against teachers who may inflate (or deflate) students marks due to teaching methods, personal sentiments, or personal marking methods. If a teacher suspects their students are going to do poorly on the diploma, perhaps their teaching methods need to be reevaluated.
So long as one has been provided the necessary materials, I believe that it is possible to achieve a standard of excellence on these exams. In layman's terms: It's not rocket science.
Zak Turchansky
Honestly, I am much more concerned about getting the marks required to get into university than having the right "skills and attitudes."
What matters even more is if you are applying for foreign universities, it is unfair to be graded lower that the students with equivalent knowledge from other provinces.
Simply not being able to achieve the marks needed to enter university due to the "generally more difficult" exams prevents albertan students from their potential opportuinities to prove that they are better.
As an international student who chose to come to Alberta for my high school education, I can't help feeling somewhat regretful about the decision. If I ever knew about the fact that the Albertan diploma exams were harder compared to other provinces, I would have thought about the decision a little more carefully.
50% of your mark? That is ridiculous! Like Jen said above, why would our government want our marks to drop 10%...? A little less weighing system would be nice, but who am I to care anymore because I am in my final year of highschool, and this will be my last time writing these diplomas and I WANT the kids younger than me to go through what I have went through. I have one other thing to say. What if you have a HORRIBLE teacher that does not teach you properly and they make their own tests that in comparison to a diploma exam are so much easier, that someone would think you were cheating all year! The teacher I had skipped a unit in Chemistry last semester, how stupid is that? It's not like that unit was NOT gonna be on the diploma, how could the teacher know that! This semester in Biology was no different. She decided to teach us the hardest unit of BIO 30 last, so in the last 2 weeks before diplomas we were rushing to finish DNA stuff!! How is that fair? Then she gave us a unit exam that dropped students marks by at least 5% (my friends dropped by 10%!)... You can't always blame us doing bad on diplomas when in fact, it could be the bad teacher teaching it. I have my BIO diploma tomorrow, wish me luck, cause I'm 100% sure that my 70% average is going to go down to 50%... THANKS Alberta!!
I question the fairness of the Social Studies 30-1 test administered in January. The students who wrote this test were the first students to study the new curriculum. They had teachers and exam markers new to it as well. When it came time to prep for the diploma, it was really hit and miss. The sample written part did not correspond to the real test given. The multiple choice had questions that required advanced reading skills and decoding of tricky wording.
However, the true unfairness is the fact that Alberta Learning posted the January test on their website with sample student responses. This gave students writing the test in June an enormous competitive advantage over the students who wrote the exam in January. [Competitive because these students are competing for scholarships and seats at universities.] They were able to prepare for the exam, knowing what to expect and how the markers would mark their work. They also had the advantage of being taught by teachers who had been through the curriculum during the first semester. If the mulitiple choice was the same test, then the June students would have known a general idea of where the areas of study should be.A more fair way to have handled this situation would have been to have kept the part A secure until after the June date.
Finally, I know many students took a position on their January position paper, requesting a rescore. To me, this is Social Studies at its best. Students were compelled to debate an issue and follow history makers with taking a stand. It seems unbelievable that some/many rescore marks were 15% lower or higher. How could this happen? I feel students receiving lower marks for this particular test should have their higher mark recorded.
I do not think that the diploma exams should be worth 50% of the course mark. Many of the students worked very hard during the year and tried to raise their marks up to their highest possible standard. However, when a 3 hour test ends up being worth what an entire semester of work is, something is wrong. High school is supposed to help prepare you for university. Rarely in university will you ever find one single test worth 50% of your grade. So how is this fair to do it in high school, especially when this method is only used in that one important year?
Another thing is why is the average set to 65%? Most class averages are about low to mid 70's. So why have a test designed harder to make marks drop lower, especially since they have such a large weighting? This doesnot make sense. Also, if everyone in the province writes this, and the average is set to 65%, this average must counter all the people in IB, AP, and all the people in other more challenging curriculums, since they often find the diploma much easier and therefore do better on them. How is this fair to all those who may not be as good in that particular subject, especially since it may need to be used to get into university, college, or wherever else people may go?
It is also not fair that there is no previous testing for new curriculums such as the social studies curriculum. As I took this course in the first semester of the new curriculum, I did not find it fair. Teachers were only just learning the curriculum themselves, and we did not get as good an education as if we were to take it a few years down the road when we would no longer be guinea pigs. There were also no diploma practice questions that we could use to help us figure out if we were on the right track or not. This gives us a much lower advantage than all the other years, and trying to compensate for this through one diploma exam does not do it justly.
I agree with many of the decisions that Alberta Education has made over the years- especially getting rid of the written portion of the science and math exams. To put it simply, when I wrote my Chem 30 diploma the year before, my final diploma mark was 85 but I got a low mark on my written portion.
However, I must disagree with the value of diploma marks being 50%. It is a ridiculous thing to have half of your mark determined by two hours. A student in high school feels so much pressure because everything they've done during the year doesn't count for much unless they do well on the diploma exams. I know many people who have had excellent marks, studied hard, then blanked out when it came to a particular topic on the exam. They've aced that part before, but then can't remember a thing about it. There are no real second chances- even the rewrite is so far into the summer that most students would be working full time by then. Do they really have time to study?
Diploma exams also downplay some things. In some courses, something the student studied for a long time may only have 8 questions on the test about it. Not a topic- the entire unit!
I know that the value of the exams must be high, but I don't think it has to be completely half. If it was even 45%, I think it would be fine.