What does your son say the issue is?
Looking at your first thread, I wasn't clear if he is only in a 40 minute pullout for gifted? If that is the case, is it possible he is being bullied or teased in his main classroom because of the pullouts? Is it possible that someone (GT teacher or regular one) is giving him harsh criticism that has him withdraw.
Perfection also can inspire work avoidance and sandbagging. It is much easier (psychologically) to set out to fail than to try and fail; particularly bad if faced with a feedback/critique style that is condescending or when positive salted with negatives.
