Pretty much any book that is going to have useful information for sex ed, which is taught at around ages 10 to 12, is either going to be useless or sufficiently graphic for hormonal pubescent kids. Back when I was a kid, the go-to source for accessible nudity was National Geographic. Also, there were kids who would read the National Geographics to learn about the world (which included places with different taboos than us). Should the education of some be hampered for the sake of the ignorance of others? Alberta says yes.