No, I don't think kids should be learning about homosexuality in school at all, whether it's "it's ok" or "they are going to burn in hell". It's not a schools place to either push moral or religious beliefs. They are only supposed to be pushing academics.
In practice the vacuum gets filled as human beings are moral/spiritual creatures. They cannot be pure scholars, they have hearts and souls. You remove God from their hearts and Satan takes His place.