How do you discipline a 6 yr old who is misbehaving at school when he comes home?

My son is in kindergarten. He is behaving badly. He is being very disrespectful and a little violent. We have ed him when he has done this at home. The teacher does not think that him after school is the correct punishment. I have tried taking away items, not being allowed to watch TV, etc. Nothing seems to be working in getting him to behave.