One way I deal with violence is to get the students to list all the possible reasons for fighting.
To protect one's body, to protect someone else, to protect property, to take property or land, to get revenge or vengeance, to protect one's honor, to humiliate someone, to intimidate someone, as a form of rough play, or in a matched fight or performance.
I then try to examine these reasons historically, so students know that they are part of what is, and has always been, normal. I sometimes pull out a twenty dollar bill and ask if students know who this person is. President Andrew Jackson got into at least 30 duels (to protect his Honor) (some say as many as 100), he also abducted his wife and chased her former husband into the woods with a knife.
Discussing duels helps students understand why they want to fight, why it's normal, and also why it is inappropriate. Most fights at school are attempts to humiliate or intimidate someone. If students understand this they are much less likely to get into fights.
Once we have had this discussion, I can sometimes stop a confrontation between students by asking them if they would like to perform a fight to the death for the rest of us.