Maybe if we didn’t divide people by sex and assign gender norms from birth we would learn how to interact before puberty without sexual objectification.

Part of the problem with teenagers - particularly young teenagers - is that they're very self-obsessed and mood driven. Like, it's easy to say "just raise your kids better" when you're not deal with the bubbling caldron of hormones kettled inside a head that literally physically hasn't fully developed the faculties to process the emotions.

That's not to defend gender norms. But it's certainly easier to go with the "Lord of the Flies" flow than it is to bend the tidal force that is clichish, selfish, horny, and often violent teenage base tendencies.

It would make navigating teenage years a lot easier if we started than with a gender/sex diverse social group

It's helpful when teenagers have a group they can empathize with at an early age. But that doesn't work at a summer camp full of people who haven't met before.

Kids routinely can and do self-segregate along age and appearance and behavior. It takes a lot of human labor to undo the natural impulses of young kids.

And that means hiring more people, which costs more money, which cuts into the profit of the camp owners.