Sounds like a frustrating experience. Are you sure that your DS would cooperate and do the work if given a higher level at school? Or could the problem possibly be something else (maybe in addition to boredom)?
Very much worth asking. Apart from boredom/inappropriate work, I would ask
--(because of the SPD) whether autism spectrum disorders were considered/ruled out. (Lots of gifted people on spectrum are missed in the diagnostic process because their strong language skills aren't "typical.") Kids with ASD often resist schoolwork with a "what's the point" attitude.
--are there possible LDs or ADHD? If a child has trouble with handwriting or decoding or any other component skills, they often will refuse work.
--what is your child like at home? Will he do chores willingly, or do you get the same "important to you, not important to me" attitude?
I'd really look at all the pieces, not just the giftedness.
