essbee, IME a change of school can do wonders - as you know (I assume, since I've posted on other threads about) my son got a bit of label about his behaviour at one school. And the school also had a playground playfighting problem. This was a bad combinaton. The little boys organised themselves into gangs and the gangs fought each other. My son kept nagging me to buy him football shin protectors that he could wear under long socks so when boys kicked him it wouldn't hurt! Anyway if he came home hurt, I knew the teachers would say my son was no angel either. Not much action would be taken - the problem was such a general one.
He changed schools when he was 7 and he really benefitted from having a fresh start. No one had preconceptions about his behaviour. Playfighting hardly happened at the new school either. My son suddently stopped talking about getting back at so and so, being hit by so and so, the gang he was in etc. etc.
Your son being hit by sticks is awful - can you show the teachers the marks today? I am surprised they did not fill out an accident form if he got hurt like this while in their care.