Someone in highschool may realize the consequences but that doesn't mean they could handle them if they happened. And a lot of people (not just teenagers) say they understand the reprocusions of their actions but don't fully grasp what they are and the effect if would have on their lives. Like the 1% chance you could end up pregnant (this is considering you use protection). Not saying sex is wrong since there's probably a 20% chance you could get in a car accident. Doesn't mean you don't drive. But you'd better be prepared for that 1%
because no heterosexual individual brags about how they only love the opposite gender and not their own.
I don't think the probleis that 15 year olds are possibly not mature enough to emotionaly handle sex. But the fact that even if they ARE and understand the possible consequences is that if those concequences were to happen who would be taking care of the child? Certainly a 15 year old doesn't make any income and is not at an age where they can even partialy support a child. That is where I think the "teenagers shouldn't have sex" argument should be. The reason I as a 17 year old don't do anything is that fear of the 1% chance that something would fail and i'd end up pregnant. Sure it'd be enjoyable but its nothing that can't wait since I plan to marry my boyfriend in the future and he feels the same way.