This is a conflict of absolutes, in my opinion. Parental rights over Government dictation of how to raise children can only exist with certain limitations. Parents can't illegally abuse their children and the state has a right to remove children from abusive situations. Similarly, the government can't dictate religious beliefs nor deny teachers their religious beliefs. People are entitled to believe whatever imbecility masking as religious they desire. The best way to meet in the middle of these two fundamental principles, in my opinion, would be to allow parents who object to teachers informing them of children expressing interest in what some religious nut case believes is the duty is to sue them in court for violation of the parents' belief that their child's religious freedom to think for themselves was violated. A few massive fines to school systems and individual teachers might damper this outing desire.
Alternatively, perhaps weighting down such teachers with chains and throwing them in a river somewhere, awaiting God saving them and thus showing His agreement could also determine what God believes.