I agree with broadening his social skills AND having down time as well. I think Scouts/Cubs would be really worth a go as its got lots of different things that appeal. I'll be putting Ds into Cubs as soon as he is old enough.

I also agree with not putting him up in primary school. I was always younger than everyone and that just annoyed me. The work was easy and (guess what!) ended up talking though everything. I ended up being given extra work to shut me up.

I also lept a year in high school, but at my own insistence. I left one school to skip a year at another but it didn't work out as I ended up sick and lost my entire last year at school. It would have been far better for me for my original secondary college to have put me up a year there. No one (except my homeroom teacher) noticed that although I was always kicked out of my yr 9 classes, I was totally at home in the yr 12 classes that my homeroom teacher used to drag me to so I wasn't clowning around outside the room....

So maybe look at advancement in yr 9-10, where you (now) can take extension classes. My DD was doing yr 8 maths in yr 7, it was no big deal...