Per definition, grading by a curve usually means that the students are assigned grades based on the statistical distribution of the test/exam results. No matter what, say 20% of students will always fail, and only say 10% will get a perfect mark.
I see a number of serious problems with this, and I fail to see anything in favor. In my view, for a fair system, the following are necessary; and neither are fulfilled by grading by curve:
- A test/exam should have clear and absolute rules and requirements. Here, the students do not know what are the exact requirements to get the result they desire, as the point limits are, obviously, only known after the test/exam.
- The grade of the test should directly correspond to how much of the course material did the student learn and understand. The fact that the same ratio of comprehended material can give an A in one year, then a C in the next year, tells that the requirements of the course itself are also very unclear.
- Similarly, the grade should directly and absolutely reflect the knowledge of the student. An A+ should worth the same every time in the same test. But here, the grade only reflects the student's knowledge relative to class members. It can't be correlated to the amount of learned knowledge.
- The grade should only be influenced by factors under the direct influence of the student. Here, the mark depends on factors like how "bright" are the other students, how much effort they put into preparation, and even on whether they cheated. Hence, the student's mark is influenced by circumstances completely outside of his control, and unrelated to his knowledge.
- No matter the collective results, a given number of students will always inevitably fail. If almost everyone is a genius, there will be the same number of failures as if everyone did poorly. Good students may fail, and bad students may pass. In a similar way as the point before, a student shouldn't be faced with the negative, possibly serious, consequences of failing, just because by chance there were a lot of very bright students in the class.
- Also, it creates and encourages an unhealthy and harmful class dynamic. Ideally, the students help each other in preparation. If an otherwise smart student doesn't understand some part and is roadblocked, others would explain. If a student missed a class due to valid reasons, classmates help to give and explain the missed material. But learning by curve creates an artificial race situation, where the students are actively harming themselves by helping others. Decimating the collective amount of obtained knowledge, this goes against the very spirit of education.
All these problems, and I'm struggling to come up with any argument in favor of grading by curve. In fact, I see only two cases where it may be used, and both of them are a fault of administration:
- The department expects an exact number of students to pass the course. This is against the spirit of education IMO. If a student is good enough, he should pass. If not, he shouldn't. Regardless of others.
- The responsible teacher failed to set exact, absolute, and clear requirements, and/or is lazy or unable to do so. Because of his fault, the students are exposed to an unfair grading system.
Am I missing something here? Are there any objective arguments in favour of grading by curve, and what are these? If not, or they are weak, what are the reasons it's still used, apparently widely?