Hey guys so I too have been having the same problems and decided to do a few experiments. I know someone else said that if you have a high aptitude test score that you won't have classes so I based my experiments on that. My sim has very high skills also including logic, athletic, cooking, writing, socialization all at 10.
Test1: I had my sim take a test and then go off to uni. The class schedule did not come up nor was she able to attend any classes. Though by the end of term she passed with a C and was able to graduate with a diploma. This was two terms/two weeks.
Test2: I had my sim skip the test and just sent her off to uni. Once again there was no class schedule but she still was able to pass the term with a C, though she didn't earn her degree because of the length of term which was six day/one term I'm sure if it was 2 weeks she would have.
Test3: I went to another family who didn't have any skill points and sent them off to uni without taking the aptitude test. Once again there was no class scheduled and she still passed with a C. This was only a 6 day/one term.
It's still a bug I'm guessin, seeing how the sims don't have a schedule but they all pass with a C. for the test 2 and 3 I didn't do the two weeks/two terms so if someone wants to try that out go for it, but I assume it'll be the same. I'm not playing like this because there is no way I can just go to uni just to party...though that would be cool in rl lol.