Alas, there are idiots out there who have “fun” dangerously manipulating parked bikes at school. My daughter had already had her front quick release axle loosened last year (we replaced it with a fixed one), and just on Friday the brake cables had been slipped out of their housings:

The way some peoples' brains work, how they are hooked up to pursue “tee-hee-giggle” nastiness is quite sad. Maybe they get a thrill, maybe they feel some kind of peer pressure towards and acceptance from the deed, but they really don’t think things through for the risks they are generating for other individuals and - by extension, in the worst case - their families.
There’s something of that in the Trump movement - some just don’t care any more and get that “tee-hee” thrill when it goes worse for others.
Societal norms are important, as are support structures for all, including those - hopefully just temporarily - teenagers seeking dumb-ass thrills.