Degrees of Lewdity is text based with some animated sprites. It's set in an entire town rather than a school but it does simulate it with pretty decent content.
The other I could think of is
School Game which fully simulates it along with some RPG elements.
Koikatsu! is probably what you're looking for, the character creation is very in-depth and you can either make your own characters or go through some threads for card sharing. The life-simulation is somewhat okay-ish in my opinion, it gives you dates and other events within the school while the characters run around doing their own things.