Sports are usually the only extracurricular activity that receives drug testing, at least around here, and even then, only if there is suspicion. I've never seen this to be a deterrent if someone was going to use. Hiding one's use from the night before is not difficult at all.I'm late to this party, but I know when I was a kid it was a lot easier to get than alcohol. Now that I am older and wouldn't buy from kids, it's a lot harder to get.
CC, I saw your figures about teen alcohol vs. marijuana. It shows that one is more popular. There are other factors now too. Kids get drug tested in order to stay in extracurricular activities. Alcohol leaves the system quicker.