Of course I have heard the phrase. (Was that a bit of condescension? Prolly.) But those kind of people dislike having anything to do with the law. Suing them would be worth it just for the hassle factor. They would pee their pants just from being served. They need to be made uncomfortable, if they can’t be made accountable.
Sorry, no condescension was intended. I have, on plenty of occasions, had to explain the "blood out of Turnip/rock" phrase.
"Suing them would be worth it just for the hassle factor."
Given the demographic makeup of the school, it's likely that the victims are impoverished also. It's unlikely that an attorney is going to take this case on contingency if the defendants parents are penniless. You would be surprised how frequently in these kinds of case, the perpetrators or most plainly culpable actors aren't named defendants in the action.
Think about the Dennis Quaid baby case. Quaid didn't sue the hospital or the nurse(s) that were directly responsible for the injury to his twins. He sued the pharmaceutical company, instead.