... the caretaker had a dog.
Kids picked on that dog for months, while the caretakers weren't watching.

One day the dog, up until that time friendly and well-behaved, went psycho, and started randomly baring its teeth and snarling, even attacking the kids.
Its behaviour had changed suddenly and instantly.

I've seen the same thing happen with school kids.

Humans are pack animals - we have a psychologically profound requirement for love from our own pack.

Constant harrasment from our peers deeply violates our psyches, and makes young humans with still-forming minds, extremely unhealthy.

I guess all here already know all of this.
Its deeply shameful and absurd that so many teachers lack this basic knowledge.