In the UK
Most drug use is totally recreational, for raving and having fun. I know a couple of people who sniff speed (Speed in England is amphetamine powder, not shitty pharms like Adderal) to study, but very few.
MDMA and cannabis use is (In my area anyhow) incredibly common amonst 17 - 20-odd year olds. Up at college (When I was in it) just about every person I interacted with used MDMA (If only monthy or so, where as my lot were/are doing it weekly) and a lot used Ketamine and Cannabis too.
Ketamine is incredibly popular, no one would even think of using heroin, methamphetamine (It doesn't really exist in the UK anyhow), I only know a few people who've done Tramadol, crack, etc.
In my area there's a public park where ALL the drug users, whether they're in college or not, hang out to trip, do Ketamine (Very popular at my college, I and many many others were sniffing it during college 3 or 4 times a week), get pissed, smoke weed, all while blaring loud techno, raggatek, Jungle, Hip Hop. Drug use is a very casual thing here, not in the sense that people do it rarely, in the sense that if your mate sees you in the street tripping, wonky as fuck or stoned as a kite he ain't going to be surprised, and drug use (I'm not just talking cannabis) during the work/college week is also incredibly common.
I probably attended over half of my classes off my face on ketamine, a few even on MXE :L
Drug availability. I can get my hands on litres (50g) of Ketamine, ounces of MDMA, large volumes of 2cb, lots of cannabis (All the time, from the one 50-year old dealer whose house I frequent very often, not just to buy either, just to hang out), can sort ounces of MCAT, lots of pills, (Weak, unfortunately) LSD, lots of 25c and 25i, every so often changa/DMT, mescaline.
Just spent the last 60 hours non-stop sniffing MXE, 2cb and MDMA, was absolutely beautiful.
It's beautiful!