My problem with grading on a curve is this:
What if the material studied is something very easy to test, for example the whole class is learning simultaneous equations in algebra.
At the end of the learning period (x number of weeks) there is an exam on the subject.
What if all the kids get most of the questions right, and the results are in the range 92-100.
Should the kid who gets a 92 get a D or F?
Alternatively, what if the whole class stinks at it and the range is 50-59.
Should the kid with a 59 get an A?
I remember one time in a chemistry class I took in college, one of the students asked the prof if he grades on a curve.
He said: “Well, a C has a curve. So does a D. B has two curves. No curve in an A. F likewise has no curves.”
I think it would be rare for an entire class to score ultra high or ultra low on a test, or more importantly, over the course of an entire semester. And if it started to steer that way, teachers could ‘calibrate’ the difficulty level. Like any competitive event, people tend to spread out.