Feedback to the student about their level of mastery of the coursework (relative to the coursework itself, not the rest of the class).

Of course, that doesn’t have to be a letter; percentages along with specific corrections would do as well. But once there’s a convention people often use it.

Grading students relative to each other gives different information and probably not precise across cohorts at that.

It isn’t a zero sum game. It’s possible for all students to get As and for that to still be a meaningful measurement of skill.

Grades don’t show your ability relative to others, they show your mastery of a set of knowledge and skills. You mastering something doesn’t prevent your neighbor from also mastering it.

It looks like grades may be different depending on when you were born.

https://en.wikipedia.org/wiki/Academic_grading_in_the_United...

In my day, Rank-Based grading was the system, but not just among the students in a specific class -- it was based on historical numbers. The same course was taught for many years so it was easy to get that longitudinal view.

Especially in secondary and high school, a 'C' meant you were average for the students who took the class. The tests had questions of differing levels of difficulty. If you couldn't answer the difficult questions, you clearly didn't "master" the material and therefore couldn't get an 'A'.

People with average ability would be expected to get an average on the test, so a 'C' would still mean you learned the material adequately and could move on to the next class / grade.

Because it indicates "this student has a good grasp of subject X".

If everyone at Harvard exits with a good grasp of Calculus, that's useful information. If only half of people from BU graduate with a good grasp of Calculus, that's also good information. BU and Harvard don't need to have the same proportions of A students for it to be a useful data point.

I think the root problem here is that some people see grades as an absolute measurement of whether someone has mastered the material, and other people see grades as a way to rank students relative to each other. If you believe the first, then it should be possible and expected for a class to be able to get all A's. If you believe the second, then it makes sense to widen the dynamic range such that you get a clear rank ordering.

To catch people who don't meet expectation. Tests are written such that A means "you performed at the level that was expected of you" and B-D are varying magnitudes of failing to do that.

> A means "you performed at the level that was expected of you" and B-D are varying magnitudes of failing to do that.

Incorrect! An A just means you got 90% or better accuracy on tests/quizzes. 60% means you earned enough to move on to the next subject.

Therefore, "What's expected of you" is to get a D or better. Otherwise only an A would be a passing grade.

This is just semantics. When tests are written to where the expected grade is an A then less than that is coming in under expectation. Also I don't know any school that lets you move to the next course if you got a D. It's enough to say you passed but not continue.

In America there's a saying, "D means Degree" or "D means Diploma". D is the bare minimum passing grade.

You're not going to get into a prestigious school with grades like that but community colleges will still take you.