My viewpoint is probably going to be pretty unpopular, but here it goes.
I think society's concept of sex is convoluted and destructive. In its essence, sex is a biological function that results in children. That is all it is "meant" for; pleasure is a side-effect that encourages the instinct to procreate. We've instead reversed things and defined sex as a fun act instead, one where physical enjoyment is the endgame and a resulting child is the undesirable "side-effect" to be circumvented. This concept of sex and sexuality has allowed it to become a commodity to be advertised, sold, and exploited on a grand scale.
Now imagine that you have a child on the cusp of puberty, hormones already difficult to manage on their own, being bombarded with imagery of this fun social act that everyone is taking part in that would satisfy the very desires their coming of age has awoken. Sex sells and our youth buy into it with a fervor, because what else can they do when it's always shoved in their faces? It becomes the goal of many relationships and interactions in the public sphere, even going as far as defining social standing (he's a "player", she's a "gardening tool" [you know what I mean haha], etc. etc.).
The rampant resultant promiscuity of this hypersexualised society has lead to all sorts of problems that would not be an issue if sex were viewed in its initial sense: an act that fulfills a biological role. Sexual disease, teen pregnancy, child support issues, etc...these are plaguing youth that have no idea how to handle any of it and our solution? Let's just teach them how to be safe and how to deal with problems as they happen.
It boggles me how backwards this approach is. You've cut someone and then offer them a band-aid, why cut them in the first place? It's like putting a can of gasoline right next to fire and praying it doesn't spontaneously combust.
Sex should not be trivialised to a popular pastime. It should not be a commodity. Sex is an act for people ready and willing to deal with the ultimate result should they choose to want it. We don't trust children with alcohol until a certain age, they should not be trusted with sex either. If that seems like an unfair stance, it's only because we've made sex into something fun and cool that someone can be deprived of rather than a process that fulfills an instinct most teens are not ready to think about.
If any "sex education" needs to take place, it's simply defining it as one of our bodily functions. This in conjunction with de-sexualising our society would render all of the problems surrounding youth and sex a non-issue.