Kinhaven has a full symphony component that every camper participates in. It’s not just a chamber music camp - it’s got symphony, chamber ensembles, and large chorus, all of which perform weekly.
The supervision there was appropriate for high schoolers (and for middle schoolers, for the junior session). Not too overbearing, but not lax enough for them to get into trouble. And it was all so much fun that my kid loved it there, would have gone back every summer if it had not been interrupted by Covid.