The following was copied from Summer Programs - Cause Prioritization Wiki. Feel free to edit at will.
It seems that summer programs (e.g. CTY/SSP/SPARC/ActionQuest) have a huge number of socialization benefits (especially to teenagers). People socialize with people they otherwise wouldn’t socialize with, and they provide bonding experiences that otherwise wouldn’t happen (especially when they are no longer psychologically restrained by the fear of their parents - ). and many people would do a lot better if they attended more of them.
Cost is what holds many back, but do summer programs really have to cost so much? It seems that attracting people to lecture at the summer programs is what costs money, but given how poorly most students learn from lectures, are the lectures really necessary? Why not just have basic supervision to prevent them from doing anything too irresponsible and let emergent behavior develop?
These could be especially beneficial to homeschoolers/unschoolers too. And they especially need not be limited just to teenagers. Adults can benefit just as much from them. In a sense, Burning Man is a summer camp for adults, but does it just have to be Burning Man?
Also see https://www.quora.com/What-is-the-best-summer-camp-in-the-U-S-and-why
These programs may not need to just be restricted to the summer either.