Tl;dr at the bottom
This is NOT a religious discussion. Yes abstinence is a part of some religions, but this is about which method you teach in schools. I aslo don't care which road you take. Personally I will probably abstain from sex until I can father a child, just incase mistakes happen.
Middle Schools and High-Schools all teach something about sex. Either they have a Sex-Ed class, or they have a speaker come to teach to the class at whole. Schools can go down either method. They can choose to educate about sex and how to take safety precautions, or they can choose to teach abstinence, which is abstaining from sex until marriage.
As I see it, abstinence teachings are inferior. Why might you ask? Simply the fact that if a horny teenager wants to have sex, then someone telling them to wait for marriage won't really change his mind. What you can do is to educate him on how to be protected. No teenager wants herpes and any teenager with a small amount of intelligence knows that is not a time to bring a child into the world.
Another thing I think abstinence teaches, is that marriage is all about sex. Marriage is about love, and yes, sex and love coexist, but you can love, without having sex. You can have sex, without loving the person you're having sex with. A lot of teenagers that grew up in our community here got taught this abstinence education. There was someone's son who married his high-school sweetheart straight out of high-school. They wanted to have sex and thought that marriage was a good option. This early marriage caused a lot of stress, which in turn caused them to break apart after many years together.
These people who teach abstinence also have babies right out of college, when they don't know whether they will have a job or anything 9 months in the future. Things are too uncertain in this economy, and at that age to have a child. I see them making the dumb decisions more than I see any teenager at my school, at least those related to sex.
Tl;dr: Sex-Ed is better because it teaches how to be protected, while abstinence doesn't, and even makes another message where marriage is all about sex.