Well my parents don't let me, but my dad has told me that he'd rather I smoke weed than be getting drunk. I do it anyway, and I wish I could just be honest with them, but my mom at least has this opinion as if it's an evil mind-rotting drug. I'd rather live without the stress but I'm too much of a pussy to just come out of the hot-boxed closet.
That being said, it's the same with like 70% of the kids I know who are my age (11th grade). So even if you don't let them, they're going to if they want to.
Also I keep a 85%+ average in school btw, I have one and soon two jobs and I pay for all my own shit, and I consider myself a responsible kid, I stay away from drinking 99% of the time, with the off couple drinks I'll have once in a while (every 2-3 months at most).