I feel that personally, the biggest problem that plays a huge variable in every teenager's life are their friends.
Yes, there's also various media factors like dirty magazines, TV, random exposure from all kinds of content.
Let's face it. The USA tends to view females as sexual objects, this is said before and given as a fact many times.
Other various countries are developing or nowhere near the economics of the US. They would tend to follow US customs due to the fact that the US holds a high value in trade, barter, and mercantile. Women are generally viewed as second to men in those places, which the Women's Suffrage period ended in our states sometime ago this century. So figuratively speaking in this case, women are not highly desired for the same reasons. It's the laws and common culture & society that influences people. Laws are used to govern people, and in this case since people are protected under law, sexual desires and impulses are regulated to an extent.
But let's not get into that, it's a complete veer off into another topic.
The way I view the average teenager; who completes K-12 through a public US education system - typically, most are interactive with the schoolmates and friends they get to be around as they get older.
Their schoolmates are the biggest influence on what the child does. Particularly what to wear, what to eat, what's cool, what to do, what's gossip. Though I'm sure the average child does not get into the gossip part until junior high or high school. That's where they start getting into sexuality and those subjects.
I'm not completely sure, but for science courses in the USA Education system, these days it is mandatory to have a sexuality or health class starting junior high. I remember my science teacher taking over that task back then.
But anyways, average kids from here on get influenced by the friends that they are with, if any. Say that John has a few friends, Jane, Joe and Jill. They are all studious types, following a strict schedule set by their parents. So for them, it's school, study, books, homework, soccer, 1 hour of TV, visit grandma on the weekends. The only influences for these to start getting ideas would occur from either: (not limited to, but leaving exotic occurrences out of the variables)
a) Friend of their friends - their social network
b) Media - Television, Playboy, Movies.
As you can see, this inhibits their hormones big time due to the fact the options of "getting ideas of sex" are limited. If they caught their mom and pop in the middle of it, then that might change things around, but let's follow a general flow line for that example.
On the other hand, the fact that many kids do not complete their public education properly because they drop out, don't finish their work, don't study. In these, but not necessarily all - they are possibly interacting with the wrong things during their growth, and predominantly exposing their experiences with all their school friends. Remember, facts and studies tend to show that K-12 dropouts are not uncommon, which was a 1-in-4 or 1-in-5?. That means there's a 25% chance that one of their friends are a dropout.
Now I understand that not all kids drop out for the same reasons. Some could be for family issues, domestic problems, etcetera etcetera.
Again, just wanted to say it for all the parents on here - Your child's friends make the biggest impact on how they act when they grow up!
When my future kid is near to be a teenager like 11 or 12, I would like to teach openly about sex education and prevention of pregnancy, and the same subject (more deeper than a basic) about sex and drug with her/him because the open commutation is pretty importance to me.