The great leverage which the BOE holds is the fact that they are 'protecting' all the children, a charge which they cannot and should not take lightly but seem to relish as a challenge to find the extremes. One cannot overlook the tragedies of late to see why they might feel the need to exercize such extreme control.
Yeah, this is the root of the school's "rights." A school is considered to be the acting parent, with surprisingly few limitations, while the child is in its custody. But this reflects how our society has been moving, where schools are the ones that raise kids starting from an obscenely young age (I think the common practice of putting kids in day-care when they are 6-weeks old is criminal, but that's another issue).