My personal and unproven theory is that most school staff are bullies/cowards themselves (two sides of the same coin). They have a instinctive fear of punishing bullies and dealing with the blowback from their parents because the odds are good that bully parents will raise bully kids. Victims are often socially awkward and an easy target to punish without much risk to the teacher.
The dynamic is laws and standards of evidence in court that make expulsion of problematic kids too costly, for example IDEA 2004.
Video and audio evidence is the only lawsuit proof mechanism to prove the problem child needs to be punished. And this applies in the adult world too, see cops and body/smartphone cameras.
And with these kind of settlement amounts, everyone is going to look to minimize their liability and maximize their plausible deniability, including teachers, taxpayers, admin staff, and the school district itself:
https://www.nbcnews.com/news/us-news/family-bullied-teen-die...
Someone getting jumped? Video helps a lot. Someone being subtly poked and prodded for months on end who then turns around and punches a bully in the face… who is now expellable at the bully’s parents’ whim even though every individual in the school knows what happened?
And let's be real here, this includes the teachers. I, and most of my peers, thought our teachers were ignorant to most of the drama in school. I went back a couple of years after I graduated, and learned that teachers generally know exactly what's going on, who is in what relationships, what fights are going on, and yes, who is a bully.
There’s some wisdom here. What I’ve heard before is that teachers enjoy the feeling of school popularity and the power that comes from it. Perhaps the fact that teachers in Japan also engage in bullying validates this theory.
And in tiny societies, just like in the real one, there will be injustices that need to be managed by some mechanism other than just “don’t go outside, put cameras everywhere.”