What helped me not get so mad at people is convincing myself of the fact that they are confused. People do dumb things when they're confused. They have knee-jerk reactions, they conform with others if they're laughing, they make jokes, etc. Have him explain his stutter to the class. It will be hard, but it's the only thing that made the anxiety let up in me. Get up and let them hear you stutter. Tell them about it. Tell them you can't control it. Make a little joke, "you'll have to wait a little longer to hear all my great ideas." Say thank you and sit down. Then everybody knows. The teacher as well. No one will be sitting there thinking "gosh he needs to relax" or "what the hell is wrong with him?" Everybody is better off, especially your son who can start feeling like a normal student because he will no longer be hiding something that is impossible to hide.