If your third-grader is spending an hour and a half on just her math homework, for instance, that's way too much. “Keep track of her time for several days, then talk to the teacher,” suggests Dolin. Sometimes teachers honestly underestimate how long an assignment will take. If your child routinely works long hours because she's struggling, also talk to the teacher. But if she seems to be slaving over homework because she's a perfectionist, you may need to discuss a reasonable amount of time to devote to an assignment and then clock her.