"...the teacher going by their own rules/morals..."
You are right. And that, unfortunately, is the real world. Who hasn't had a boss/stupervisor who made their own rules up as they went along. Maybe experiencing that in school will help prepare the little brats for what comes next. I had one teacher who would what you with the narrow edge of one of those thick, brass tipped yardsticks, whenever she felt like it. Did me no lasting damage that I can see...
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OBG