Of course not. I think I had a woodie my entire teenage existence. LOL
However, doesn't talking about sex in a classroom of teenagers somewhat excuse it in a "you can't help yourself, so this is how you do it correctly" kind of way?
I think it depends how you teach it honestly.
If you teach it going, literally "Look, we know you kids are going to have sex. We know you're going to do this. All we ask is you do it safely, and this is how", yeah, that excuses it. You're going to have a number of kids that would've previously possibly abstained for longer than they will now because of it.
HOWEVER
I also think if you go there and say "Having sex is bad. Abstinence works every time. Just don't have sex and you're fine. IF you have sex you're almost definitely going to get the girl pregnant and probably going to get an STD. Just don't have sex, okay, sex is bad unless you're married. Don't do it." then you'll also have problems. There's going to be kids that do it now just to spite authority, to be rebels. There's also going to be kids that honestly were trying but puberty, hormones, and being a kid get the best of them and opportunity arises and not only do they not know what to do but they become so paranoid over it it makes the situation more unhealthy for them mentally.
NEITHER way is optimal. Both I think are pushed by people who...to be frank...don't give two ****s about the kids and actually care about their side "winning" the political point.
What is optimal is telling kids that abstinence is the best way to avoid the legitimate and realistic consequences, emotionally and physically, that can come with sex and abstaining until later in life will be of benefit. However teaching them that when that time comes that they do engage in it that they should go about it in a safe manner, both in regards to birth control and actions. By actions I'm not talking about "how to give a blowjob", but the risks of overly promiscuous sex, the fact some STD's can be transfered in other ways than conventional sex, the benefits of a committed relationship, etc. Finally, stressing that while sex is a large responsibility and can have life altering impacts that it is not bad, or evil, or wrong, but simply something that is not to be taken lightly and frivolously.
Those that have a legitimate chance at being inspired by an abstinence message are in large part likely to still be inspired by it in such a course. So for those kids, you do them a service by not forgoing suggesting that abstinence at a young age is best.
Those that are unlikely to be touched by an abstinence message are given knowledge on how to be safER when/if they do what they would've done anyways under abstinence only education, which does a service to them by increasing the likelihood that a portion of them does it safER.
Those that are likely to do it simply to rebel have less of a rally point now than in abstinence only. Those that are easily influenced by the acceptance of adults wouldn't be as apt to go forth and sow their wild oats than in a primarily birth control focused curriculum. And those that could honestly go either way but are average teenagers, filled with hormones, that may not even plan for it to happen but it does have knowledge at least on how to do it safER and remove some of the possible mental issues of them torturing themselves for doing something horrible, evil, wrong, etc.
Notice I use safER because it should be stressed that "safe sex" is not guaranteed, but is more akin to air bags and seat belts. They offer protection and increase the likelihood that the bad stuff doesn't hit you, but that doesn't mean it is full proof.