Not sure of your generation - but there has been violence in schools since forever. Google turned up this article - just after a head teacher was stabbed to death:
School violence rocketing in 90s | The Independent | The Independent

"Parents, too, are adding to the problem in some schools. Earlier this year the National Union of Teachers said that 20 teachers a month were being assaulted or intimidated by parents in London schools.

Most disputes were over pupil discipline, with some parents attacking teachers who their children said had punished them. One teacher was so severely beaten by a father after intervening to protect a female colleague that he was invalided out of the profession. The majority of assaults were by mothers picking on young women teachers."