If 80% of students get A, it's very weak motivator if you are top 10% student. Essentially there is no point in working harder than some arbitrary pretty low th

If 80% of students get A, it's very weak motivator if you are top 10% student. Essentially there is no point in working harder than some arbitrary pretty low threshold. Most subjects has unlimited depth so it should not be too hard to design test with reasonable questions where no student get everything right and you can do normal distribution for grades (something like 5% A+, 10% A, 40% B, 30% C, 0-15% F)