This has been discussed before, but we are pretty much all in agreement so it doesn't warrant much discussion. This is already addressed by society in general, too, with support for sex education and safe sexual practices.
Your presumption that concerns about sexually transmitted diseases mandate restrictions based on age rests on a false premise: the idea that restrictions based on age are relevant to the question. It is not age that causes STDS, but pathogens. What we need are not age-based restrictions, but measures that will prevent these pathogens from spreading.