LC, good points, however, before this discussion goes off tangent on whether or not sex education is needed in Pakistan or only in the West, I would ask that discussion stays on teaching/talking it to the kids regardless of their geographic location. Thanks!
Sorry fg, I was trying to get to that, but since others are also probably going to invariably comment on the relevance of this issue in the west and not so much in a country like Pakistan, I do think it's important to emphasize that these problems exist there too. I distinctly remember my O-levels biology teacher not even wanting to cover the book chapter on reproduction and we were asked to go over it ourselves. Such is the state of affairs there... so the lack of a pertinent education in schools is all the more reason to take it up at home.
In any case, just from personal experience, I'd say parents need to proactively address issues about sex before the child reaches puberty. That being said, the actual education leading to that point needs to start much before. We need to overcome our hesitation in explaining the differences between the male and female bodies to our kids... and be more open about bodily functions early on. Don't tell your kids that children are born in flowers or drop from the heavens etc. - but make them appreciate the miracles of nature and the human body early on... I'm not saying at 3 or 4 years of age, but by the time they're 6 or 7 or so, they should be able to understand these things.