Here's an unsurprising stat for you, teens are actually smoking less pot in Colorado now than they did before it was made legal. [Source]
According to the study, pot use decrease from 22% in 2012 to 20% in 2013. While that's not a HUGE drop, it does go against what legalization opponents say would happen should weed become legal nationwide.
Opponents of pot legalization always claim that making it legal would lead to higher use situations by teens and young adults. They get this "fact" from the 1990s when teen use of tobacco was rampant. That's just not true anymore. In 1995, nearly 25% of 12th graders smoked, now it's only 9%.[Source] They assume automatically that teens can't control themselves, and are just defaulting to a life of smoking like they did back in the 90s.
So it's unsurprising that the amount of teens using weed is also declining. It also makes sense that the number of teens using pot is going down after the legalization. Everyone remembers what it was like to be a teen. You do something because it makes you cool. Part of the "cool" factor, in the minds of teens anyways, was always that it was illegal. So if you used it, you were a bad boy or girl. So cool. Now that element has been taken away.
Of course just because the facts point to a decrease in teen usage, doesn't mean the opponents of legalization will give up. We know these people. They'll just make up some new facts. It's just the way they roll.