I want to give her a name which really depicts her cruelty and close-mindedness, but I feel like it'd create a language barrier for anyone watching who didn't speak English. And nobody speaks.
The teacher was actually a lot different in concept- she was a far heavier, but considering she was the only "antagonist" in the story, I didn't want to give out the wrong message. Her role is to put the three protagonists in detention for various misdeeds. Of course, what she doesn't know is that their "misdeeds" are either not their fault, or she misunderstands the situation. She issues detention first and asks questions later.
And she's convinced she's always correct.