I\'d send my kids to a school that teaches them these things at such an early age without any hesitation. by the time they are in their teens, their hormones are already kicking in, and they start to get all giggly and start to take the piss when such things are discussed.
By getting them to learn about it from such an early age, and getting them knowing the the consequences of their actions (pregnancy, disease etc), I think it will have the right effect. If such a thing was implemented globally, it would probably help lower the rate of increase in teenage pregnancy and disease transferral.
So, to be honest, if you ask me if I would be happy sending my kids to a school that teaches sexual education at such a young age, I would say yes, I would be more than happy to.