Why do we finish high school at 18?

I don't know if this is the correct subreddit for this question, but why does seemingly every country has high school ending at 18? Why did almost every country agree that the optimal age to enter college was 17/18/19? Why not 21, when you're more mature? Why not at 16, when you're younger? And it seems like almost every country has the same age "cutoff" for college, so it doesn't seem to be a cultural thing. So what makes this age so special. Sorry for my bad English, I'm not a native speaker

Submitted April 27, 2024 at 08:23AM by Traditional_Pin5583 https://ift.tt/NlMKotZ