It's normal (in my view) to want to understand how the world works, which includes about sex. I think as females are a little more complicated than males, and as there is often more of a taboo about talking female anatomy, if there is not a Christian way for this information to be communicated, boys will turn to other means to obtain the information, which may involve pornography, but certainly will not include the clear boundaries that God puts on sex (i.e. reserved for marriage).
My point was really if even pastors are too scared to quote verses the bible speaks plainly of (e.g. Song of Solomon 4:5) this spreads to the parents and teachers in Christian schools, and they in turn don't speak plainly or clearly about sex to their children or students (really a parent's job in my opinion, but in this fallen world, Christian schools can be the next best thing). The children then seek out the information through other means, which doesn't have the same safeguards and cautions that scripture provides. I don't believe scripture prohibits learning about sex - it restricts sexual activity to within marriage. When the prohibitions are put on the wrong thing (e.g. learning about sex), natural curiosity will overcome this, but then nothing is left for where the prohibition should have been - engaging in sex outside of marriage.