Lunamoth,
You'll meet many administrators and teachers who hear from other parents how gifted their kids are. You have test results and your son's verbosity to support yourself. If your son isn't in the meeting, then the test results will be the one thing to help make sure you are having the right conversation.

I hope you can get him into a sufficiently challenging coursework where he can continue to fly. And don't let them make writing a barrier to his correct placement.