The Sims 3 Tips

Homework help
If your sim is too stressed or too tired to finish their homework, call any other sim that is able to help. Then, before the helper sim gets there, delete the help action from their action menu. The sim that couldn't do their homework will now do it without help.

Try and finish homework right after they get home from school. If you don't, wake the sim up earlier than his school wake up time (Usually 7:00am)and then finish the homework.