We have been working very hard with Danny to help him name and manage his feelings. We explain over and over that he can be angry and we understand that he is angry, but he cannot be rude or yell at people. He usually responds by shouting, "But I'm angry!"
One of the tools that we've used for him is something I developed in my classroom and call a "feelings paper." The kids can mark what they're feeling - everything from frustrated to angry to excited to happy to sad to nervous - and sometimes they choose all of the feelings. Danny gave me a feelings paper at least once a day, maybe more, EVERY DAY for the first few months of this school year. All of them said he was angry. Usually in big, bold, capital letters.
I have been so proud of my young staff. Although they are mostly in high school, they do not lose their tempers with him. It's actually almost unbelievable how calm they are. He yells at them and they respond politely. He throws papers at them and they don't react. They are continually patient and kind, far after many professional teachers would have lost their cool. I think they really do understand that he's having a hard time and needs kindness modeled to him.
UPDATE: Since I've written this, there has been an incredible turnaround in Danny. Many of the staff have commented that he "seems like a normal kid now." What they mean by that is that he is not furious all the time. He's no angel, but he is spending time playing instead of screaming, doing his homework most of the time, and usually not being rude to people. When he is rude, if you pull him aside and talk to him, there's much less yelling and much more of a conversation. He smiles a lot. He takes compliments. He usually doesn't hit his sister at Harbor House any more, and he uses the words "please" and "thank you." He looks happy a lot of the time. This is a complete turnaround.