It seems that you feel that the testing doesn't reflect him at all. Did you comment this with the tester? Did she say she had noticed something unusual?
You could still advocate for him or look for yet another school. You might consider retesting next year on the WISC. I wouldn't submit a DYS application even with a strong portfolio showing his advanced work because you still need to show the IQ part of it.
One possibility that seems to work for many kids is to supplement at home or "afterschool". If he likes his school otherwise, he has friends in there, etc. I would probably keep him there.
