It's not that I don't understand asynchrony. But when you have a child who's known for getting involved in others' mischief in class, who got involved this time in a minor way and contributed to class disruption a bit, the teacher wasn't out of line in briefly scolding him.
In most third grade environments he really would be expected not to contribute to in-class mischief, no matter his age. If his teachers will be fine with contributions to others' disruptions etc. at his public school, I guess that's something, but the teacher here still wasn't out of line, and it would still be good if he
could begin to adapt a little. The right response isn't
anger furious peevishness; he wasn't traumatized and the teacher has to maintain order, and merely communicated to him what he should begin to know. The words "You're bigger than him" aren't enough to get
angry furiously peeved over.
Maybe a good solution would be to get him switched to a more grade-appropriate group at camp. If that were done and the same thing happened, perhaps sans the sizist comment

, would you still be upset?