http://www.acosoescolar.info/padres/index.htm (help-line from "Protégeles" association, http://www.protegeles.com ) has useful resources and information and can be contacted to get support. People in general and teachers in particular too often choose the easier way (it doesn't matter, it's normal between kids and so on), but it does matter and it is not normal nor acceptable. The school must protect the kids. You are doing the right thing. ¡Mucho ánimo!