I think it's how abstinence is taught that determines its effectiveness. You have to give kids information, not just tell them that they shouldn't have sex until married, but if they do, use a condom. Communication is key. Nobody advocates occupying kids bedrooms, but teaching them to have healthy respect for themselves and others, as well as knowledge of sex and all that it entails is essential. From what my 17 year old tells me, the sex ed in schools these days is really just 'how to' information.