Oddly, this is one reason to send kids to public schools. I understand and respect parents that want to protect their children. However, my position with parents was always this: Kids are going to be exposed to the crap the world wants to dish out. Faulty views on sex, drugs, philosophical issues, religion, etc... At least when they hear that crap in public schools, parents still have enough influence and ability to teach them right thinking. If kids are not exposed while parents are still near enough to counteract the crap, they will initially be exposed to it when they enter college, the workplace, etc... By that time, it's too late for parents to intervene.
Not an argument without holes, but one worthy of parents' consideration.