> it’s whatever policies the school has.

so the school takes on that responsibility, as deputized by the parents.

Kids don't get unfettered access to the streets while at school. They can't take their bikes and ride out at will. What makes the internet and devices any different? The devices provided by the school should be lockdown-able, and kids should not be provided their own device unless there's a parental lock (which is enabled during school hours, and is similarly locked down).