What steps should I take in filing a potential lawsuit against a teacher and the school district?

My daughter is a 5th grader and her teacher has been verbally abusing her as well as other students. I have complained to the principal and the school district, but was told they are trying to work with this new teacher. Also I have reported that the teacher grabbed my daughter by the arm and filed a report with the principle. This past friday the teacher again embarrased my child and verbally abused her in front of the cl. The principle was told of the nightmare by my daughter, and now it appears action has been taken and teacher removed from school. However it has taken more than half the school year to see results. The friday incident involved my daughter as well as another student. The parents from the cl came into the meeting to vouch for the behavior and advised they did not want to say anything because they did not want their child to be retaliated against by that teacher. Myself and another parent whose child had been tormented are wanting to know what our rights a