Noone has mentioned web porn yet. The issue of sex education has recently changed ... one report I heard recently suggested that the typical age of first viewing web porn is 11.
The influence of web porn is not to be underestimated. Someone earlier mentioned the prevalence of rectal gonorrhea in some communities. This will probably be a major trend shortly. Anal sex has come to be seen as virtually fundamental. Even family sit-coms like '2 1/2 Men' treat anal sex as if it is the best, a special treat that all men should expect from their girlfriends. Certainly that is how Charlie Sheen portrayed it.
This is not because anal sex has always been universally popular, it is because the porn models get paid double for anal penetration, and that has resulted in the practice appearing as almost fundamental to sexuality.This then shapes expectations. This is just one example of how web porn is reshaping sexual mores.
So your 11 year-old is probably looking at porn on the web, and assuming that this is ordinary human sexuality being portrayed. This effectively means that web porn will define human sexuality for the next generation. The 'Are You Over 18' button is all the kids need to press.
The typical progression for web porn users is an escalation of the level of 'kinkiness' (for want of a better word) over time, and that is catered for. A kid viewing web porn now will get the impression that sex is basically a physical event, and that anal sex and gangbangs and BDSM are the options on the menu. The notions of intimacy and communication are not included in the visual world of web porn.
If parents and teachers don't discuss all this with kids, web porn will be the defacto standard for sex education.