I have heard of this problem before,I have also noticed the two go hand in hand ,Did you ask the school what had happened to make him angry and how they handle it,there are boundarys he has to have, gifted or not.Are there some situations that trigger his behavior, and how do you and his Father deal with them. Apart from school work does he play a sport and go out has he friends ,sometimes these children become rather solitary,. You can always ask for other Oppinions before they diagnose him.