I teach high school. The faculty men's bathrooms aren't locked. A few times a year I walk in and find the toilets overflowing because somebody took a roll of TP, mashed it, and shoved it into the toilet--then took a crap and flushed a couple of times. From time to time during lunch it's meals and utensils.
Probably not a teacher. Or principal. Oh, gee, a lot of the students, esp. resentful, angry young men, don't like being there and take out revenge on the mostly black and brown custodians. Sort of warped sense of justice. The faculty just go a couple hundred extra feet to a bathroom kept locked (but we have keys for).
Any chance there are a lot of angry, resentful men at the detention camp in FL? Except in their case, it probably is guards having to clean up their mess.
Seen it infrequently on airplanes, too, where some idiot just didn't realize that all the he (I'm guessing a 'he') didn't realize that the toilet wasn't a trashcan.
Overflowing, that's a different issue and one that's easy to manage.