Continuity mistake: When Miss White is writing Mrs. Heimer on the chalk board, the camera shows Kevin/the class, when the camera comes back to her, she has a different sweater, hairstyle, and her name is written in a different spot. I'm not sure if this is some kind of flash to when everyone comes back to school after summer, or an error.
Continuity mistake: When the gym teacher is drawing on the chalkboard, the kids ask him to draw the whole woman. He does, and the word "ovaries" that he had written disappears. It reappears differently in a second cut.