Symbolism, Imagery, Allegory
Even though the world of Wayside doesn't seem to stick to regular laws of physics, they have a well-known code for disciplining students: Mrs. Jewls writes the name of any kid who misbehaves up on the chalkboard under discipline; if the student misbehaves a second time a check goes next to their name; a third incident gets their name circled and the student sent home early.
This may seem like a very concrete system, except Mrs. Jewls hardly ever writes the correct person on the board—unless they're Sammy the dead rat. The discipline list seems to stand for rules in general, and the fact that the authority figures who enforce the rules are so often wrong about who's to blame.
If anyone knows about teachers blaming the wrong person, it's Todd. "Todd," Mrs. Jewls says at the beginning of Todd's chapter, "you know better than to talk in class. You must learn to work quietly, like the other children" (5.3). And then up it goes: Mrs. Jewls writes Todd's name on the board under discipline.
The problem is that Mrs. Jewls blames Todd when other kids next to him are behaving much worse. When Joy yells at the top of her lungs, Mrs. Jewls says nothing—but when Todd responds, "Will you please let me do my work and stop bothering me!" (5.18), Mrs. Jewls puts a check next to his name. Why does Mrs. Jewls single Todd out for punishment, especially when he's trying to be a good student? It's silly and over-the-top, but it also reminds us that sometimes teachers can be seriously wrong.
And because the discipline list comes up repeatedly throughout the book, it also reminds us that Wayside isn't an ordinary school. While it's fun hanging out in Mrs. Jewls's classroom, good luck not getting sent home on the kindergarten bus.