The problem these is that there is too much noise in the signal. Given that so much of your grade is based on sitting a single exam, the variance in your perfor

The problem these is that there is too much noise in the signal. Given that so much of your grade is based on sitting a single exam, the variance in your performance on that day makes it pointless to differentiate between students who got for example 87% and 89% on the exam. All you can say is that both are "very good" at that subject, but you cannot meaningfully judge which is better. On the other hand couldn't grade saturation be seen as a good thing, if it indicates that more and more students are successfully mastering all the material they are supposed to master.