I'm really sorry to hear that your daughter is being bullied at school! I think that it is understandable and reasonable that you are concerned about your children's well-being. There is a great deal of research to show that the consequences of bullying on victims are significant and severe in terms of emotional trauma. It is critical that the school staff take a very active approach to the problem and stop the bullying immediately. Many schools have developed thorough and comprehensive bullying policies. Clear policies typically have a description of the responses and consequences to bulling on-campus. Thus, everyone is in agreement as to how these sort of situations should be handled. As far as you know, does your children's school have anything like this in place? If not, perhaps the school board could take this on.

As far as additional measures, I think that you should make an effort to make yourself available to your daughter. Continue to listen and validate her feelings and reassure her that you are actively working on the problem, and you will do everything in your power to make certain school is safe for her. Write down and document the dates and times of bullying experiences and present this to school personnel. Listen to her feelings about her experiences of victimization. Help her develop active (but nonviolent) strategies for managing bullying in the moment. For instance, there is research to show that children who firmly yell, "Stop!" and walk away to tell a trusted adult often dissuade future bullying.

http://www.education.com/reference/topic/TeenYears_MiddleYears_Bullying/

Good luck and keep us informed on your progress!