I would have gotten the "board of education" at school, then again when I got home.
A parent or teacher that refuses to address this type of behavior is negligent in their duties. We are all affected by the few who don't fulfill their responsibilities - most of all the child.
It appears that the parents refused to use corporal punishment and handed responsibility to the school who then did the same by calling the cops. What a sorry lot.
"Spare the rod, spoil the child." is not a joke.