I think children in their teens should hold off from sex. It is addictive and it has many pit falls, many responsibilities to bear unnecessarily at such early ages. Lives have yet to mature and clouded by a perilous obsession is not what one needs. Once old enough, have at it. You will know what risks you take by knowing all the rules of the game. It is hard enough that you will soon enough be whoring for survival on this Earth while engaged in a war with your species.