Well as a former educator I must say I really don't recommend telling children to fight back and it's not because I want kids to take abuse. There are reasons for this mainly if a child retaliates against another all it does is encourage more violence and often the child will have disciplinary action taken against them which could include loss of recess, a parent teacher conference or even in or out house suspension. That being said there are some things that you can do. My sister a parent of 5 children has done a few of these things with her children. See we live in Philadelphia so you can imagine how turbulent the schools are here. In fact the school my sister's children go to is quite disruptive. She had been up to the school many times demanding action and in one case a boy even inappropriately touched my niece. What she did and what you can do is if you aren't receiving satisfaction from the classroom teacher then request a one on one conference with the teacher stating your concerns. I would keep a log of who is bothering your child with dates and times so you can share this with the teacher and this will also be a documented record of what's going on. I did this all the time when I worked in the classroom that way when meetings arose I could point dates and times and action I have taken with a particular student's behavior. If this meeting proves unsuccessful by any means meet with the counselor at the school. The counselor should have some resourceful information for you as well. Some schools even receive funding to have teams for Bullying so you should check this out as well as peer mediation another excellent resource when students don't get along. If you have exhausted your resources with the teacher, counselor, peer meditation, and Bullying Prevention Team then your next conference should be with the school's administrator preferably the Principal or Vice Principal. If nothing comes of this take it to the local District Office. Every school is overseen by main headquarters or a District Office. Find out who is above the schools superiors when the steps here don't work. I hope this helps if you have any more questions feel free to ask me. Thanks again. Great question by the way.