He has found that he gets attention through this behavior and he is asserting his authority and rebeling against other authority, in other words he wants his way at all costs, and he is too yung o realize he consequences of his actions. You must be creative in setting up consequenses that will get his attention and make him want to change his way, as well as finding ways to remove hi frombeing the center of attention, and be able to ignore his bad behavior
Have you tried asking him what makes him angry? Have you spoken with his teachers to see what they have to say about his behavior, what they think is triggering it?