I don't think they should though. I mean, obviously you have a right to instill your religious and moral beliefs in your children, but I don't think that extends to taking actions that carry a very real and concrete threat of serious harm or death, just like you can't beat the crap out of them because you believe in firm punishment. Children aren't their parents' property, they are human beings with their own rights, and since they don't yet have the capacity to make their own decisions we as a society have a duty to protect them. Usually we delegate that duty to the parents, but when the parents are failing in that duty I believe society has an obligation to step in.