Terribly interesting that you seem to believe that your children's peers are likely to be a better influence than an adult teacher. Terribly sad if it's actually true, but it's almost certainly not. Even given the rather notable exceptions of teachers sleeping with high school aged kids, sex is hardly the worst you have to worry about. The other children are offering drugs, illegal activity (trespassing, and street racing were favorites in my day), and sex. Not to mention that peers are far more likely to reject adult supervision, and adult ideals of behavior.
That's all ok though, because we all know your kids haven't listened to you in 5 years, and they aren't going to start now. Your kids get their culture from TV, movies, games, and other kids, you as a parent have only a minimal influence over this, especially if like most people, your kid has been raised on multi-media with little or no oversight.