You are correct it is probably learned behavior from his brother and possibly brother is still doing it at home. Have a chat with his older brother and ask if he can 'cool it"the problem may continue till you get a handle on that.Can the teachers tell him to stop the behavior as he does it there, perhaps they need to have a consequence when he does behave in a disruptive mannerSpanking wont help it is only re-enforcing hitting patterns. The sense of Humor is good ,focus on his positive side and praise him when he does something right.Work on the 16 year old,