He may have a chemical imbalance or some other mental health problem that is striking this anger in him. It sounds like hes far from neglected but it also sounds like he knows that his behavior gets him attention also. But it really doesnt sound like that's why he's acting out. I think u should take him to a mental health doctor and have him atleast evaluated. Therpist arent for everyone, especially those who's behavior is harmful to himself and others. If it isn't controlled now then when he is older, not only will it be harder but his behavior will get worse and may lead to other problems...such as dropping out of school or even more dangerous, hurting someone else. Which may land him in a place where ur unable to protect him. It may seem like alot of work, but his future and the people in his future will be affected in a negative way if this isnt fixed soon. He cant help himself so u have to help him and there are a range of disorders that trigger this behavior, one being bi-polor. And most can only be controlled through medicine.Take him to a doctor,soon.