There is definitely stuff going on for him (out of school)... he's living part time with a bi-polar mom in "recovery" who is in an emotionally abusive relationship. Its really a long story - too long to go into. While we both (dh & I) have a very positive relationship with his mom it is hard to see dss acting as her caretaker and her putting him in that position by telling him every negative thing that goes on in her life. That's still a situation we have yet to resolve. We want him to be part of his mom's life. I don't think taking him away would do either of them any good.
If he were my biological child I would have pulled him out of school a long time ago. Unfortunately that is one option that is just not possible. We are planning on unschooling our daughter in a couple years and perhaps he will see what its like and decide he wants to try it. Right now he says "no way!!" He thinks being homeschooled means having no friends.
He's really a great kid, very personable, smart, etc. I just see a child who has an aversion to learning school stuff. He has a very strong personality and hates to be told what to do. When it comes to learning things that interest him (videogames, music lyrics, characters in Magic cards, etc) he does great and has no problem. I might add that I find it completely normal to have no interest in learning things that are meaningless to you... I really see him as a great unschooling candidate and wish there was a Sudbury Valley school nearby!
We are willing to try anything... perhaps try the backing off approach for a month or two and see what happens. Thanks for the thoughts!