My sister is getting bullied at school, any suggestions in what i could do to help?

Go above the teachers and speak with the Principal and tell them what is happening. Make them help you she is only in 4th. grade and if the principal does not help you then go over there head to the superintendent and if that person does not help you then go to the school board and bring it up in a public meeting and force them to help her. Always keep climbing the ladder higher and higher you will reach someone and get this to stop.