No such thing as "schoolies" in the UK where I did my schooling, and I don't remember such a big thing being made of (high school) graduation either - I always thought that was about finishing your university education. There was no school ball either - thankfully my parents didn't have all the expense associated with that.
"The brain is under construction until about age 27 and the older members of the tribe have a duty of care to protect the young, such as the hoon,from their own idiocies."
Exactly. And that's why none of our teenagers were allowed to go on leaver's week. My 17 year-old son (the youngest) has just finished school. In between looking for a part-time job, he hangs out with his mates or they come here. There is no alcohol involved - heck they might lose concentration playing League of Legends :-) None of our teenagers questioned our stance on leaver's and seeing all the trouble that happens, were happy to stay at home. They are all well-adjusted individuals, doing well at uni/work and it seems the parental discipline is paying off. Our kids - our responsibility.