Have one of daughter's teammate's high school aged brother who gets dropped off at the bus before dawn every morning. The other morning it was 21 degrees and cloudy and he showed up in thin athletic shorts and a thin long sleeved t-shirt. The most I ever see him wear is a hoodie and thin warm up pants even when it is below zero and windy.
I often wonder if this is ever a point of conversation in the morning since the parent who drops him off clearly sees what he is wearing.
I just had an epiphany a few years back about the phenomenon of high schoolers just wearing hoodies on arctic days...
Way back when, when I was in high school, I had to share a locker. The locker was a normal size, but trying to fit two bulky winter coats was a chore. (And I did wear a winter coat to school. It was an exceptionally cold winter my senior year) A lot of HS lockers I've seen nowadays are smaller/skinnier than what I had.
Now, I'm not excusing the student you saw from wearing long pants or jeans...that's just teenager stupidity.