This problem is easily solved. Why is there a discussion? No discussion. Immediately send her to the principals office. The principal calls mom or dad to come pick up their daughter. That's right mom and dad, now you have to leave work to come pick up your child who isn't following the rules. The way you parent is to set boundaries (rules). Communicate those rules. Kids are going to push the boundaries. Which should be met with immediate consequences. No discussion, no counting, no time out, boom, consequence. And, I know, the parents are part of the problem. So mom and dad have to be held accountable too. If junior is a problem at school then that should cause a problem for mom and dad. Hold the parents accountable.