Plenty of boys and girls going out when I was a teen, a fair few (but not all) having sex, only one teen pregnancy that I ever heard of- and that was the daughter of the Baptist minister getting pregnant on a language trip to the US.
The only case of herpes I knew of for sure was someone contracting it from mouth sores whilst still a (very young) virgin.
I think there is plenty of evidence that very early sexual relationships and teen pregnancies are not so much about sexual freedom or even sexualisation of society.
Instead, they tend to happen to vulnerable young people who do not foresee a very interesting future, so they don't bother to take care. These were precisely the kind of young people who got pregnant when they shouldn't in Victorian times too- and for all I know probably in the Middle Ages too.
Teens who feel good about the other relationships in their lives, and who are looking forward to a career and an interesting life, tend to approach the whole thing with a good deal of caution (starting later and taking more precautions), quite regardless of the conservative or liberal views of their parents. If you have something worthwhile lined up, you're not going to want to blow it.
I was interested to hear from dd-conveyed gossip that the girls (and boys) who started very early in her school were not actually the very popular or very bright ones, and that early sex did very little for their street cred: if anything, the other girls thought it made them look a bit sad; it high-lighted the fact that they weren't very imaginative about other aspects of their lives. From my private observation they also often seemed to have the kind of parent who worried about their sexualisation in a very prurient way and who did not have a very close relationship to them in other ways. This is such a thing as a self-fulfilling prophecy.
So I'd say if you want to keep your children safe, don't worry too much about the messages of society- concentrate on your relationship and the encouragement of their dreams. Dreams are the safest thing you can have as an adolescent.