Kids are not free at school, in case you noticed :)
They're not free to think? More's the pity. It's nice to know we'll continue treating all teenagers as if they're complete morons.
Perhaps education is the key to solving problems, and would allow for freedom and personal choice, rather than simply banning anything that might ever cause the slightest harm to anyone. In fact, I seem to remember a form of institution dedicated to such education. What were they called again?
If you're honestly implying that our children - some of the oldest "children" in the world - are completely incapable of figuring this kind of thing out until the same age at which they magically become capable of understanding sex and alcohol, then I think that's very patronising.
In any case, drugs are not allowed in society - in general, when substances are addictive and have adverse side effects, it's best not to feed them to kids.
I think there might be a little bit of a difference between sugar and heroin, ta. But then, I'm one of those children-hating bastards who thinks drugs should be legalised.