Abstinence only states have the highest rates of teen pregnancy. Because guess what: people have sex. Not just adult married people, but adolescent people who, although perhaps not mature enough to successfully care for a child, are physically mature enough to bear one.
The irony here is that those of us who will teach our kids the realities of sex and how to protect themselves from unwanted pregnancy and disease, including the fact that the only certain protection is abstinence, aren't the ones who are concerned about having our children receive this instruction in schools. We already talk to our kids about the realities of sex and make sure they understand the risks and consequences of sexual activity.
The kids I'm more concerned about are those that receive no sex education at all other than abstinence (and perhaps the occasional Sunday school lesson in which someone licks the frosting off a cupcake). Because when these kids find themselves in a situation where their partner says something ridiculous such as that floating is OK, they won't know better. And I'd rather see these kids stop by Planned Parenthood before than after.