Amanda from the Golden Boot Soccer office here. I’m not sure where you’d be coming from, but our annual AC Milan camp in Fairfax always has a strong section of high schoolers. We group by both age and level, so your son would definitely have a group of peers.
We use indoor and outdoor facilities and players work with both AC Milan coaches and our own professional trainers. It’s a large camp, but individual groups are small so everyone gets a lot of attention.
More info here:
http://www.goldenbootsoccer.com/summer-camps/a-c-milan-summer-camp.html , or please feel free to call the office with specific questions.