I don't have advice since I went through that with my son when he was a lot younger and what I did wouldn't carry over to an older child. The school was entirely unconcerned, I ended up homeschooling. But I wanted to chime in for solidarity and sympathy. You are not alone in this.
I'm reading "The Turned Off Child" which looks promising in the first chapters. It might help you. Also "The Explosive Child" and corresponding website livesinthbalance.org are a fabulous resource when children are stuck and acting out (or in).
