It sounds to me like your son is communicating something to his teacher and to his friends. It is up to his teacher to lovingly not judge him but redirect him or teach him how to greet his friends or work with materials in a respectful way. I have a little boy in my class who likes to throw the materials on the floor. After a conference with his parents and a game plan, it was clear that we were not all being consistent with him. His grandmother was way too lenient and not following through on setting limits with him.
Children crave direction.
Our game plan was to redirect the throwing behavior. In my classroom we have a bean bag toss. That is appropriate for throwing. Classroom materials are to be worked with gently and with the utmost of respect. In Montessori education we are instructed to show and continually present different developmentally appropriate exercises to the children over and over again.