> Now kids can't have these accounts, so they can only access youtube without signing in. Meaning zero parental controls and monitoring

This sounds like a device-control problem. Banning social media and then regulating devices in school should go a long way towards defusing the challenge.

Even with anonymous log-in, the new status quo is a release from algorithmic targeting. (If YouTube is building shadow profiles and knowingly serving under-16-year olds, that can be fixed with enforcement.) I suspect this group of kids will grow up fitter despite the reduced opportunities for helicopter parenting. There are lots of parents who never try, or try and fail, to control and monitor their kids’ online activities. Way more than those who effectively do so.