Being one of the younger ones who only finished school just 3 years ago and still have 2 siblings in high school, I can pretty much confirm just how bad the drug problem is these days. I could get drugs within 2 mins if I wanted too and it was at a private school as well. There will commonly be 2-3 groups per year groups that will be the main offenders, that group that think that there the "big boys" of the school and consider themselves as gang members (usually they say there apart of Assyrian Kings), the other group would be that group of nerds who no one expects but I tell you what they like to indulge in a lot of drugs, also the biggest myth is that girls rarely touch anything like that, they do it almost as much as the boys but there just way better at hiding it.
While sports may help, it can sometimes have the opposite effect, I was pretty decent at footy when I was still in high school and through all the school competitions lets just say I made a lot of new friends which resulted in a lot more parties and more opportunities to try drugs.
