A close friend of mine got a tattoo our senior year of high school but she had just turned 18, so it is possible that a few of the students you're seeing actually got them done legally. Naturally.....this friend of mine got a coverup for that one haha
i got my first 2 when I was 20. they're definitely more cutesy than i might choose for myself now, but they are both really meaningful.
this was my first-

on my upper left bicep, almost shoulder. sorry for the crappy quality. it definitely needs a touchup, but it's not nearly as bad as this picture makes it look

second (about 15 minutes after the first)-

on my right side
i've averaged about 1 new one a year, this is the third-

on the inside of my left ankle
fourth, and first with my current artist (who i will more than likely be going to for any and all future ones)

on my left shoulder
fifth (and technically sixth as well- got 2 of these- done at the ends of both collarbones)

seventh-

aaand eighth-

getting this one next month on my calf. pretend that it's bright red....the black is done on tracing paper because i didn't feel like wasting time drawing the asterisk when i could just print one as a reference....
after the asterisk, im gonna work on touching up the older ones, maybe altering them a bit and then attaching the small star, ladybug/flower and the raindrop into a quarter sleeve-ish thing.