Nick's parents have always had a rule in their family - "Homework First." That means that right after school, both Nick and his brother James always have always had to finish their homework before they do anything else. Naturally, Nick and his brother would sometimes wish that they could play or do other things when they get home from school, and would often "groan and grumble," but the rule is firm; "'Homework First' (is) the law from September to June."
Nick's brother is all grown up now and has gone off to college. During his first semester away, James writes home that his grades "are looking great, because when (he went to college he) already knew how to put first things first." James' declaration is proof to Nick's parents that their insistence that their boys always do their homework before doing anything else has paid off. For this reason, they are even more zealous in enforcing the rule, so Nick has little or no chance at all of getting around it.
Nick actually does not mind his family's rule about homework, because up until he is in the fifth grade, he gets very little work to do at home. In the fifth grade with Mrs. Granger, however, it is a different story, and Nick really has to discipline himself to get all his homework done so that he will have time to go out and play afterwards (Chapter 4).