Went from a small private primary school to a large state secondary school, there were 200 kids in my primary school and at least 200 in my year at secondary. Was the only kid from that school as well. Got in a whole heap of trouble, used to play truant and sit in the local library reading, was taken in by the estate cats and well... learnt a lot about life... man I'd be a good criminal if I was still out there .lol.

Your brother seems ok though, sounds like you have a good relationship with him, no need for him to look to trouble to express himself if you get me, lessens the need for him to look for respect elsewhere if he can talk to big bro about things.

Talk to the school if you're worried.