Despite the set back, Jagger has been to as many of the games as he could manage. You increased his allowance a bit, so he could afford to attend most of the home games and still get concessions. The one thing is that you were pretty strict with what he does while he's at the game. You know that he's mostly interested in watching, but you also know that kids have gotten in trouble for messing around other parts of the school that are supposed to be off limits.
The two of you discuss it, agree to some limits, and he's been doing just fine.
He was silent most of the way home, until he finally broke down and explained that the game had been really boring, so he and his friends just went over to 7-11, because their drinks were cheaper than the concession stands, and a couple of the guys had wanted Slurpees. He even still had his drink glass with him.
Whatever his reason, it was definitely a violation of the rules. Are you going to make a point of explaining that to him?