Maybe I’ve been lucky but I find the kids I encounter before puberty are singularly uninterested in sex, romance or what it means. There is a great little book (What’s Happening to My Body? Book for Boys: A Growing Up Guide for Parents and Sons and one for girls, too, by Lynda Madaras) explaining it all, and parents need to get that, leave it with them and let them take it up when they are curious. And answer all questions, when they come, very honestly. But don’t give too many details or go too far.