Sex education should be administered age appropriately. The really young children only need to learn "stranger danger" and not allowing people to touch them inapproriately. Somewhat older children need to learn the basics of the biological differences between males and females and how babies are conceived. Nineth grade on up, sexually transmitted diseases and sexual preferences (heterosexual, homosexual, lesbian). If students come forward to ask anything not in a standard curriculum, they are to be referred to their familes....period. NO MINOR is to be told that they can be whatever sex they prefer. The reason has nothing to do with the parents, but science. The human brain's pre-frontal cortex controls executive functions (i.e., decision making, moral judgement and self control). In women, the pre-frontal cortex matures around the age of 18, whereas the pre-frontal cortex matures in males by the age of 25. Because of this, important life-altering decisions shouldn't be made while a minor, and teachers should stay out of it.
In turn, responsible adults should know to restrict certain materials from minors, especially graphic materials and controversial materials. When they are no longer minors, they will have the pre-frontal cortex decision making ability to decide for themselves as to what they want.