Telling kids about the consequences of sex does not work.
That isn't true.
The stupid ones will have sex.
The smart ones, or the ones who have lived through the results of young broken families who are tipped off that fucking at a drop of the trow will cause the same thing to happen to their kids will probably keep it in their pants. Some even to the point of breaking up relationships over it, I know, I was friends with a number of these guys, few of the gals. It rather impressed me as the dateless wonder, but talking to them made their reasoning quite clear on the matter. Not a religious concern. Not a shame thing. Just straight on actual fucking planning. Working at walmart 10 hours a week doesn't cover diapers, until they had something that would, and in most cases would actually be able to support the kid as well as their parents had done, they didn't want one. Also, we all realized we had hands. Funny how that works.
The stupid ones, they have 1-3 kids now and are hardly able to care for them. The non-stupid ones are actually getting married at a rather astounding rate now that they're out of college and established(I've got like 10 people I'm still in contact with an there are 5 weddings planned this year).
And yeah, I'm calling you stupid if you fucked around as a teenager. Why? Because it was fucking stupid and you did it. Doesn't hurt that I got myself into a ball of retardation(and trust me, it is the correct fucking word here) that I still regret, no other consequences thankfully, but can we please stop this "Teenagers fuck like bunnies in heat on valentines day, why aren't you fucking yet?" business. It sends a worse message than these ever could. This isn't fear mongering, this isn't hateful, this is little more than stating the likely consequences. Ones my friends were often aware of and I managed to bungle my way past safely.
Slut shaming would be painting some teenager up on the bill board with a baby and the word WHORE written across the bottom. Posters that say "Fucking will eventaully produce children, and young parents are often unfit" is not slut shaming. It's reality. A reality these do a better job of explaining than most of the more academic attempts at it. I say this as someone who's father was 18 when I was born. It was nearly 20 years later before he was able to support children the way he wanted to, before he felt like he could offer anything even remotely close to a proper apology for having not been ready for a kid when I was born. That, that fucks people up a whole lot more than being told not to screw.