Wow! What a mixed up set of notions. There is and never will be a pure situation in any school that allows any child to free of exposure to beliefs or ideas different from what the family wishes for. To think this is possible is nonsense. My faith is strong enough, and always has been, that no matter what I was exposed to I believed in God. (I was not raised in a Christian home and I had no benefit of being taught anything about God or what it meant to believe in God. I had a near death experience that revealed to me that there was a God.)
About the sexual exposure??? Do you realize that incest occurs in no less than 33% of all homes? (Yep those heterosexual “normal” homes.) What does the school any child attends have to do with that? Perhaps what we should all be more concerned about is not a parents particular orientation or apparent beliefs, but rather whether or not the children of our society are being protected from practicing predators.
I know of a “Christian” family in which every single child, male and female, were molested by both parents. Each child was treated this way starting at the age of 5. All the while mom and dad where "God fearing, church attending, devout Catholics. Believe me those children could have cared less about school of any kind. I wonder what they think of God due to all this?
Let the child go to a place that might teach him/her about God. Let those (children) who are fortunate enough to be free of terror and horror at home be the ones that show that same love to other children. Let’s clean up our own dirt from within the supposed “pure members of the planet” with a little more diligence and honesty before we starting automatically shunning others and their children in the name of some apparent interest in purity of faith.