yes.
Often, during registration the parents sign a paper, which waives all rights and responsibilities of the school in a multitude of circumstances.
Usually there is even a clause, saying the school will not be responsible in the event of death of a student.
I would be highly surprised if the school didn’t have a document with these types of liability clauses, posted somewhere… perhaps in the student handbook, or on a bulletin posted during the time of registration.
Furthermore, if it is a public school, there is very little you can do.
To prevent future incidents, you can try to rally a group of parents to support the installation of video cameras on the campus premise, in order to catch the perpetrators… you can argue that it is for the safety and security of students- and maybe if you review their publicly printed budget you can find out what funds they could use for this. Or what funds are being used for something more absurd and less use full.