It's kind of weird that they have what seems to be accelerated curriculum, aimed at maybe a very small percentage of kids who are having sex in sixth and seventh grade while every other subject is taught to the middle. This is one place I actually wish they'd teach more to the middle.
I think the age criterion is not when most youngsters are sexually active but when puberty starts, and there is a trend for that to happen at an earlier age, as discussed in a recent NYT story
http://www.nytimes.com/2012/04/01/magazine/puberty-before-age-10-a-new-normal.html .
