University playing pool opportunity

Well, if you task your sims with something you know will take a long time, make sure all their needs are filled before you start this (they may cope with poor hygiene, but that usually doesn't help their mood). You can always have snacks on your sims. For example, just stock up on apples at the grocery store. Those may also come in handy in between classes, because there isn't enough time to go and grab some food if you don't have a gap in your schedule.