Where and how, if at all, should sex education be conducted?

I think that sex education should start in elementary school. I am a mother to a two year old and I already am preparing myself for that talk with my son. I think that if we start to educate our children when they are young we will be better off in the long run. I believe that when parents start educating there kids about sex it is already to late, their already having sex. Our children spend at least eight hours a day at school learning new things, why can't sex education be part of that curriculum? People need to come to realize that yes, sex education is a touchy subject but why not have professionals help you teach your children the right thing instead of the wrong ideas.