The thing that struck me is how you kept discounting the math interest. That counts as a passion, too!
It also sounds like school has not been great for your child. If he's an adapter--as many GT kids are--then he may have learned to keep his brain and curiosity quiet so he doesn't draw negative attention to himself. But that doesn't mean he's in a good place.
Though I am very grateful to Dr. Ruf for giving parents permission to see schools as not helpful for GT kids and permission to pull kids out of public schools, it is importnat to note that no one education option is right (or wrong) for all GT kids. Personality plays as much of a role as intelligence--maybe more of a role! So no one here can tell you that you should do this or shouldn't do that with your child. (Don't you wish someone would!) But as a homeschooler, I can tell you that the individualized eduation that I can give him through homeschooling has helped my child. It's a valid option for GT kids. Is it right for your child? Only you can say.
How does your son feel about school? Does he learn anything there? Is he happy? Is he growing, intellectually and emotionally? These are the questions I think you have to ask.
Is he damaged? Well, maybe. Maybe not. On the bright side, kids are resiliant. They recover from bad situations. But that doesn't mean they should STAY in bad situations any longer than absolutely necessary.
If you think he's in a bad situation now--and it's not clear from your post whether he is or not--then I'd say you probably need to do something for him. Grade acceleration, subject acceleration, in-class differentiation and homeschooling are just a few options that might work, depending upon your child and your school.
Has the school IDd him as GT? Are they supporting his needs and working with you? Or have you felt like they are working against your childn't interests?
If the school is amenable to working with you, then I'd start there. If you have been fighting them and feel hopeless about any chance of getting your son what he needs, then it's okay to take a different tack and pull him out of school. (Just, please, DO check your laws and school rules about homeschooling before you do this!)
It's a lot to think about, I know. <reassuring pat on the back>
