In high school in Australia, it was easy to find alcohol. Don't think there was much LSD going around (some marijuana and MDMA).
I think one difference is when you have 18 as the legal drinking age, a significant chunk of kids turn 18 while still in year 12. They could then legally buy it and then (illegally) on-sell it to their school friends who weren't of legal age yet.
In some cases parents would even buy alcohol for their teenage children. Parents supplying other drugs to their children is not totally unheard of but far less common.
I think one difference is when you have 18 as the legal drinking age, a significant chunk of kids turn 18 while still in year 12. They could then legally buy it and then (illegally) on-sell it to their school friends who weren't of legal age yet.
In some cases parents would even buy alcohol for their teenage children. Parents supplying other drugs to their children is not totally unheard of but far less common.