What made her think that she had the right to do that? 

When I was a kid, I tried my best to empathize with substitute teachers because I knew they had an incredibly difficult job. Kids were always trying to take advantage of the substitute’s ignorance and derail the classroom as much as they possibly could. I never wanted to be on the receiving end of our teacher’s lecture: «The sub told me that you were the worst-behaved class that she’s ever had in all of her years as a substitute.» Because of this, I tried to resist taunting the sub, at least in front of her face.

Every once in a while, there was a substitute who was surly and irascible towards our class in a way that impeded our ability to do our work. Old-school subs sometimes didn’t understand that the curriculum mandated we use our smartphones for assignments, so they would punish us for doing the work the way our teacher wanted us to! When a wildly strict sub encounters a class of hardworking kids who don’t want to make trouble, there are bound to be communication issues. 

The teacher in this story had a class of wonderful kids who were scolded endlessly by their substitute teacher for just trying to do their work. Not only that, but she totally reorganized the teacher’s classroom, which is way out of line. She’s missing assignments she hadn’t graded because the substitute threw them away.