Does he have any sensory issues? Some kids are sensory seeking and will do things like push and shove to get that deep physical stimulation they need. Perhaps the high-energy of the group makes him get more high-energy and he doesn't realize what he is doing? How about video tape him so he can watch himself and see how the other kids react and that this behaviour is inappropriate? Is he happy at school?
Why does he have no friends? Is it b/c of the behaviour? I wouldn't assume cause and effect. It could be he is acting this way b/c he doesn't have friends and is angry or it could be he doesn't have friends b/c of the way he acts. I also wouldn't assume negative intent on his part - if he thinks he's just playing and is not aware of how it affects others, I would label him as a bully.
What does he say about his day at school?
