D.C.
What are the repercussions to him "behaving badly" ie., acting out or loosing control? I haven't experienced what you are, but if I was, I would explain to him that we don't just do "what ever we want whenever we want" and that if he does there will be repercussions. I definitely see the 4yo boys on my daughters playground being more "ruff" etc than the girls so I'm guessing it's somewhat normal :-) Good luck!!