I think a number of reasons this happens. First of all the one of the reasons girls that are having sex at the earlier ages are from divorced parents and the girl doesn't have the father to be there for her and guide her through the times where boys are putting the pressure on her to have sex. A lot of the girl is America today lack attention that they need at the ages of 10-16.
Another reason I believe this happens is that the parents them selves are too busy trying to grow up. They might have had a child at 15-21 and really never had the chance to get out and have fun. So in essense the kids that have kids didn't have direction and help at the early age and now they have kids and they don't know how to raise a child. Because it was never taught to them. Just my opinion.
