Making your own booze as an under 21 is a bit much. When I was under 21 I drank pretty heavily and we just had a couple buddies that were 21. Kids tend to have a pretty wide and frequently accessed social network. I mean someone you know at the very least has an older sibling. I can’t really speak to drinking while still in high school as I can count the number of times I drank in high school on one hand.