I don't know if you can record or video, preferably video, the scene where the teacher forces the parents of the students, preferably with sound, and then go to the Education Bureau to complain about him, find more people who have the same experience and are forced to go with them, and even go to the newspaper to break the news. In this case, even if the teacher has a little background, he will be dragged down.
If you want to believe that there is justice in this world, it depends on whether you dare to do it or not.