Really getting into University, but...

Yeah I completely found that! My very first sim I sent to university took 4 classes and had a soccer scholarship, and it was intense! Since then, if I have a sim that I want to have a social life too, then I will do 3 classes a term and just go for longer (although the more I do this, the more it's starting to feel like university is taking too long). I think 4 classes is ok without sports in the evenings, but definitely not with. I also found that homework just takes sooooooo long - so I've found an amazing mod that shortens homework time (so sims still do it, but it frees up so much time!
https://scarletsmods.com/2019/11/15/faster-homework-university-edition/ (plus there are 3 different speeds, so you can choose what feels realistic to you :) )