### Background

In the U.S., many colleges adopt an A–F grading scheme, topped with pluses and minuses.

Professors vary in the way they assign A to F grades, but my sense is most rely on discrete “bins”. For example, some professors use relative grading and (roughly) give an A to the top third or the class, a B to the second third, etc. Others will give an A to students who get between, say, 100% and 95%, and A− to students between 94% and 90%, a B+ to students between 86% and 89%, etc.

Using discrete bins necessarily implies some knife-edge cases where a student is right at the border with the next bin, and it would have taken very little for that student to jump into that next bin and improve their letter grade by one “level”.

That would be all fine (I guess) if letters where only honorary titles, and what mattered was the actual underlying percentage grade. However, in most places (i.e., all the places I know), it is the letter grade – and never the percentage grade itself – that is attached to the student’s academic record.

This could be an issue *per se* if a student wanted to show proficiency in a particular topic and got, for example, an A− that was in fact very close to an A. That student’s academic record will forever show *very good but not perfect* for that course, whereas it should really indicate *almost perfect*. This creates understandable frustrations from students who nearly made it.

Things get even worst when averaging through different courses and computing one’s GPA, since most colleges then use a scheme like the following one: 

* A: 4.00
* A−: 3.67
* B+: 3.33
* B: 3.00
* B−: 2.67
* C+: 2.33
* …

Again, this means that the half of a percent a student needed to jump from an A− to A will have a significant effect on that student's GPA, where really, the effect of getting one more half of a percent should be negligible, regardless of the baseline percentage one is starting from.

In a world where GPAs are taken so seriously, this means that half of a percent can make a significant difference in a student’s life and career. Again, this can create understandable frustrations for students who nearly made it.

### My question

I know that there are “palliatives” to deal with the discrete grading scale and avoid some of these knife-edge cases, such as rounding up decimals. In all fairness, I don’t think those are real solutions (rounding up decimals just moves the problem from one threshold to another), but that's *not* what I am interested in here.

What I would like to know is:

* Are there any arguments in favor of using a discrete grading scheme like the one above?
* Or is just a product of history and the difficulty to coordinate practices across the vast number of U.S. colleges?

In other words, is anyone claiming that the discrete scale has virtues of its own other than the fact that it is used in so many places – creating comparability –, and that it would be hard to coordinate a change at all those places at once?