Mom & Dad are the only ones that can impart values in regards to sex education, and if you dont have any values in regard to this topic, you are headed for trouble. Sex education is vital. It starts in the very beginning of a child's life with gender identification and is a never ending process. To not teach it to your kids is negligant.
There is nothing wrong with teaching kids the logisitics and the down and dirty facts about your reproductive system, birth control, etc at school, but a school is unequipt to teach your values in regard to sex. You need to do it at home.