The best thing we did to help our DD fit in with kids her own age at school is to accelerate her a year, so she's not with kids her own age anymore.
DD does have neighborhood friends her own age (her bestie is actually several months younger), and we've taught our DD to look for common interests in whoever she's with. Her interests are wide enough that there always has to be something.
In your DS' case, I would encourage him to save the experimentation for home, and go get some exercise during recess, whether that's ball sports, tag, monkey bars, whatever. I'd emphasize that it's helpful to get out "the wiggles" and focus on school. But I'd also point out that it's what most of the other kids are doing, and if he joins in with a game, that'll help him gain friends.
