I have my second Sim in university right now. The first time I sent my Sim, her boyfriend, and best friend to school and they lived in the dorm. It was not an easy learning curve and their GPA's were not where I would have preferred, especially with my Sim having the genius trait. Her boyfriend (who became fiance during their time at uni) actually had to finish his schooling after they got married because he failed a class...
This time I have one Sim who lives in a house in Britechester and I have her taking notes during class which is the only difference from my previous university play and it's made a world of difference. She is acing her classes. So I am making a note for any further university Sims if I want them to have a high GPA.