Scare them with a real-life horror video of what happens if they let Willy in.
Yes, there's actually a YouTube video of a sudden birth on a high school lawn, at the site. For now.
You know, instead of making it all sound like fun and show 'em how to do it, why not tell (and actually show) the inconvenient, scary truth about the consequences? How would they like to have THAT happen to them? At school, or anywhere else, wholly unexpected and embarrassingly inconvenient?
Reality is the most effective slap in the face to effect teen lucidity and discipline. And to motivate 'em to keep their pants on!
Oh, and while they're showing those horror movies, they should also show true-life horror movies of the horrific reality of abortion, which is nothing less than pure, unmitigated horror, ie. the slow, piece-by-piece dismemberment of a live human being, while still inside a woman, to tell the inconvenient truth. Really, the truth is that abortion is cruel, sadistic, selfish and evil. Those who say we should render "comprehensive" sexual education shouldn't say we shouldn't include the horrific truth about everything, for to cover it up would be unethical and immoral.
Scaring the hell out of kids is, I believe, more effective for motivating abstinence and reducing unwanted conception than telling 'em how to do it.
Oh, and I don't apologize for this.