I think they need to do something about this.
I'm playing the Pleasants household and a Sim in the city rotationally. Well, the Pleasants got suspended while I was with the city sim, even though all of their homework was completed and studied on top of it. I don't know if they missed class or what.
I believe in Sims 2 the other sims got like average grades if you didn't play them. I think you should be able to pause households or something in this. The only other way I can think to play is to have all uni sims move in together. That's what I used to do in sims 2. But that defeats the purpose of being able to do uni at other world's.