Sideways Stories from Wayside School by Louis Sachar

From chapters.ca:
There'd been a terrible mistake. Wayside School was supposed to be built with thirty classrooms one on top of the other...thirty stories tall! (The builder said he was very sorry.) That may be why all kinds of funny things happen at Wayside School...especially on the thirteenth floor. You'll meet Mrs. Gorf, the meanest teacher of all, terrible Todd, who always gets sent home early, and John who can read only upside down - along with all the other kids in the crazy mix- up school that came out sideways. But you'll never guess the truth about Sammy, the new kid...or what's in store for Wayside School on Halloween! There was a terrible mistake - Wayside School was built with one classroom on top of another, thirty stories high! (The builder said he was sorry.) Maybe that's why all kinds of funny things happened at Wayside-especially on the thirteenth floor.