Make an appointment with the principal, ask for the process that was followed after your last discussion and then for an explanation as to how this incident was allowed to happen. I would expect some firm process in place and that the other student has had some consequences and clear boundaries explained as have their parents. Depending on your feelings after this I would then lodge a complaint with the dept of ed. I think you need to address your issues with the school first up - then seek further advice support as/if required. I had some issues last year and there were very clear guidelines around the child, family and addressing the issues. Make a list of your questions and objectives before you go in.