There were still his grades in school that he had to keep up with so that he would have the reports to hand over to his parents.
If he did not wish to be grounded in his own home by his parents, then he needed to be able to maintain his grades and not fall below the average in his class.
If he started slipping, then that would make his parents think that he was not taking school seriously, and they would start nagging him about how they were so busy working to provide a good life for the family, but he was ungrateful.
If they thought that way, then they would surely try to ground him or punish him in another way.
If he were grounded, then that would end up interfering with his afternoon activities once he was out of school.
If he could not go looking for lower-grade Spirits or Evil Spirits to hunt, then he would not be able to meet the requirements that would be needed for his quota for the day.
