Personally, I believe in teaching kids all about their bodies and about sex and birth control without putting a bunch of shame, stigma and moral judgements on the whole process. Give them the information they need to know in order to explore their sexuality responsibly. Part of being sexually responsible is understanding the consequences of sex. The risk of venereal diseases, the risk of unwanted pregnancy, the reality of emotional vulnerability and feeling rejected by a partner if it doesn't work out. Ask them how they would handle it they or their partner got pregnant and wanted an abortion and they didn't believe in abortion or vice versa. These are the moral issues surrounding sex that I have told my son he should have figured out before he has sex.
However, I see nothing wrong with teaching children our own moral views of sex as long as we put it out there as our own moral view and not as some sort of universal absolute. I told my son that if he is not mature enough to have open conversations with potential partners re: birth control, venereal diseases, unwanted pregnancies, etc, then he is not ready to have sex. If he is not mature enough to be living on his own in his own apartment, then he is not mature enough to have sex, IMO. If he is not mature enough emotionally and financially independent enough to pay for and look after any children that result when the condom accidentally breaks and his girlfriend of two weeks informs him she doesn't believe in abortion, then he is not mature enough to have sex. Those actually are not even moral judgements. Those are just the biological facts of life. I am pretty liberal about sex otherwise, for mature adults. To me, it is all about taking responsibility for your own sex and you own bodies and any children that result. Marriage is just a piece of paper to satisfy other people, and not necessary and it certainly doesn't force anyone to take responsibility in this day and age. It is more of a tradition than anything.
My views do preclude underage teenagers coming home and having sex after school in their bedrooms for the reason that they do not qualify as mature enough to have sex for all the reasons I listed above! I am not naive and I realize they probably will experiment to some degree but I certainly don't need to wash the sheets and light the candles for them either! I wouldn't freak out and kick them out of the house like JW parents either. I would just sit them down and go over all the above "facts of life" with them again. My views are all based on love for them and wanting the happiest future for them not on any hangups about sex or thinking there is anything wrong with it. It's kind of like drinking. For mature adults only.
I concede that according to my own criteria there are many adults who are actually not mature enough to be having sex or drinking, since they seem to be unable to take responsibility for themselves. Well that is how I talk to my son about sex and have done since around the age of 10. He is now 18. We have ongoing conversations as things come up with friends or in movies, etc. We have never had one big sex talk. I am very calm and casual and rational about the whole thing. (I think being trained as a nurse helped. I am very comfortable with talking about bodily functions, sex, etc.) It is a natural part of life and nothing to be ashamed or embarrassed to talk about. It's religion that puts that trip on to people's heads.
Oh, I also believe in giving teenagers lots of hugs and physical and verbal affection (yes, even when they are surly) so they don't feel the need to go out and start premature relationships in order to look for love and affection from the opposite sex before they are ready to handle a sexual relationship. So far it seems to be working as my son is 18 and is just now starting to have girl's as friends. He is almost supporting himself and could do totally if he had too, so while not encouraging him, I am fine when it happens. If he does begin a sexual relationship, though, I will encourage him to get his own apartment. I don't want to have to listen to him "knocking boots" if I ain't gettin any. That's just not fair!
Cog
ps: Just wanted to add, my son just came home in the wee hours as usual. I asked what he was doing out til all hours and he said, he and his friend were playing Lego's all night. I said, "yeah right", then he proceeds to pull out the new Batman Lego set he bought on sale today at the mall. He finally had to come home because his 26 year old friend's girlfirend was PO'd because they were playing Lego's all night! LOL! I guess I don't have to worry just yet!.