The headmaster is only responsible for managing these registered teachers. As for dismissing the teacher, you'd better not hold out too much hope. The teaching profession is a national undertaking. The State Compilation Committee has files. Management is based on the Regulations on the Administration of Civil Servants. You can't send them away with your words or one-sided words. Besides, even if you have enough evidence, it is estimated that no one will really check it.

Anyway, if you really want to sue this teacher, you can report the situation to your local deputy mayor in charge of culture, education and health, or to the local commission for discipline inspection. However, if you follow this procedure, you must leave your true information. If it's anonymous, no one cares. So you have to think clearly ... this kind of thing is not that simple. Maybe you will be punished in the end.