I usually give them 2 courses per term and never had a sim fail any, I think the lowest I got was a B-.
I make them do their homework immediately after the class and finish and refine any papers/presentations as soon as possible (I usually enroll them at a friday so they have the whole weekend for that), have them either study or do an activity that earns the skill of the classes in their freetime every now and then.
Yes, they have only little time for parties (but they do have them!) and are mostly occupied with study and course related stuff but hey, that's Uni!