OP I would like to thank you for the stance you are making,if it were not for people like you drawing a line in the sand then how many other countless children would have to endure this unacceptable behaviour and have their education suffer drastically,kids have enough to be dealing with,God love them without being terrified of going to school every day,it is far too easy just to throw your hat at it and leave it be someone elses problem.
Good for you and while I have no real constructive advice,beyond echoing the previous posters suggestion of going the legal route,I wish you all the best in this matter.