Tecnically there's already a cheat inside the game! The task from the teachers improving your votes.. but sure you need to do homeworks atleast!
Okay thanks i just have a old save and i never did the assignments before than and i cant get them to go up so I'm just really struggling but it would be cool if there was a cheat to up your GPA
Be sure to talk to your teachers.. no one is forcing you to have sex with them to get them started..