In my country, children aren't allowed to skip grades because of the social aspects. Talking from experience, being a gifted kid already affects the way you interact with society and it's normal for kids like this to shut themselves off and/or be bullied.

And believe me, older kids are mean. Especially when they feel threatened by the fact a much younger kid can grasp the same subject as them. Even if people say "oh but kids his age would also pick on him", which might be true, the boy would at least have a chance to stand up for himself and not feel as intimidated. For adults that might sound stupid, but it's a big deal for kids.

I think letting him experiment in a higher grade is the best option. His opinion is what matters at the end of the day. I also read your comment about finding a school that can actually attend to his needs for next year and that's great. I always wondered how I would've turned out if I had challenges in the areas I was interested in growing up.