Idahomom,
I have met plenty of kids who sound a lot like your child. I'd say it's a classic 2E situation. It's true that many/most schools and educators don't know how best to help these kids-- and that's the reason many parents (like many on this board) become the experts on how to help their children. More testing may or may not help, but a more piecemeal approach to his education may help. More emailing with teachers, more working with the school, more systems in place so he doesn't fall through the cracks. Since you said he can get a C when he's focused on one class, I certainly hope he isn't taking too many classes or doing too much extra curriculars!
Because I teach teens and up, I think most of these kids manage to fly under the radar until seventh grade or so, when suddenly the student is responsible for so much more. These kids need a lot of help keeping themselves focused and organized. Also, hopefully, there is a shred of willingness in there. Does your son want to go to college?
Also, just a sidebar, my experience has been that private schools can be no better in helping the 2E kids.