<p>My dad was a college professor (now retired) and his rule was always to hand out grades based upon mastery of the material. He had one memorable semester where he taught two sections of the same class. In one section no one did better than a B- (with lots of D’s and Fs) and in the other, no one did worse than a B. He dug around and figured out that the “good section” students were all in an honors seminar which conflicted with his “bad section” time slot. Essentially the distribution of students (and thus the grade distribution) across the two sections was determined by the course schedule maker.</p>
<p>I should point out that there was little or no possibility of cheating. Dad really disliked cheating and did everything he could to make it impossible - including having multiple versions of every test so that no more than 4 students would have the same test. Made grading more work but he was willing to do it.</p>