This was back in the early 2000s, but I did semesters as an office TA as an elective, which was really just doing rounds and getting attendance sheets from all the classes.
This let me see all the class compositions, and from what I knew of the student body, once you could see the whole picture, there were "standard" classes that were very obviously dump classes for fuckhead students, mixed with slightly above average students to balance out class grade averages.