Does he have dysgraphia, hypotonia, visual processing issues? I really think there is more going on here than ADD. Is he medicated? Is he depressed? How long has he been failing? Has he always struggled in school?

I don't feel comfortable offering specific suggestions without more details.

I think you would be wise to look into further testing with a gifted specialist who can sort out the 2e issues. Ed Amend in Kentucky, Dierdre Lovecky in RI, The Eides out west- there are several respected specialists around the country who might help. At this point, your son is dangerously close to high school when grades matter. He obviously must be extremely frustrated with his situation, and the sooner you can pinpoint his problems, the sooner you can find ways to support and accommodate. I really feel for you and for him, and I urge you to do whatever it takes to get to the heart of his issues.

best wishes-