Religious I might be, but I have nothing against sex before marriage, what I disagree with is how people don't always treat sex as something as meaningful as I feel it should be.
The age restriction on sex is mostly the attempt to put a maturity on it, an age when kids might be mature enough to handle the decision for themselves, and the age of maturity is highly debatable and varies from individuals. I'm not entirely sure about the legal age of sex but I wish we would teach our kids about things like love and meaning and sex in school, yeah I got taught about sex, but it was a technical point of view, nothing about an emotional level.
Don't see the point of either teaching them nothing, or the churches rules, neither work for the majority of today's society in my opinion, people need to know why just as much as what, if not more.