Here's a very interesting article about the "Romeo and Juliet Effect," which is basically wanting something because you can't have it. The author discusses in particular the effect (or lack thereof) of abstinance-only sex education.

The Romeo and Juliet Effect: Why Christians Keep Having Sex Before Marriage

More to the point, I'm an Evangelical Christian and we're taught at a very young age about sexual purity. Christians aren't supposed to have sex until they are married. In recent years, many have made it official by taking a pledge of abstinence. However, studies have shown that Christians, even those that take the pledge, are just as likely to have sex as non-Christians.

People I talk to are sometimes perplexed at my stand against abstinance-only sex education, but to me it's pretty simple. Until someone can prove to me that it accomplishes anything at all, I can't stand behind something on principle alone. It's like not leaving a flooding house because you don't believe in drowning. Sometimes reality forces us to examine the situation a little differently. If abstinance-only sex ed actually results in more issues like disease and teen pregnancy (and in turn, abortion), I don't have a problem getting behind an alternative.