Bureaucratic stupidity

This is an issue of parental rights. The schools have decided that they “own” the children, or at least have full parental rights over them while they are on school property (whether or no school is in session). First, one must remember that the State is allowing the schools to take this stance, as the schools themselves not only have no legal or Constitutional standing that gives them these rights or even the right to tax or enforce attendance. In this particular case, how is it that they can legally mass-medicate children (or anyone) based on an assumption that SOME of these children MAY get pregnant?