My 9 year old is at school with a child who is persistently violent. Just constant kicking, punching, throwing things, slapping, chasing other kids and tripping them up, then kicking them once they're on the ground. He can manage his behaviour in the sense that he doesn't do it when he knows that adults can see him, and he's actually very charming and polite to other parents.
Needless to say, none of us want our kids to be getting hurt. But when I started thinking about it, I realised that his two older siblings are the same. And I started wondering where it comes from? I understand toddlers lashing out in frustration but by the top end of primary school the majority of children have learned to control themselves to a far greater extent.
I want him to stop, but at the same time I would feel a lot of sympathy if I thought it likely that he's exposed to similar behaviour by the adults in his life.