Do you think the gifted academy would be a better fit than HS for your son and family at the moment? Why not look into it, explore all options and then make a decision. Does your son feel strongly either way? Would the cohort of kids at the school provide a peer group you wanted your son exposed to? What's the basic curriculum like? Do kids work at their own level and pace?
I'm at the point where I wonder whether even the most rigorous, expensive, selective etc school could come close to providing a better education academically than we can manage at home, but can see that there are some peer, sporting, musical and specialist subject benefits at particular schools.
Good luck with it all. I hope the decision makes itself easily!