Continuity mistake: When Peggy brings "Ol' Spanky" to class for the first time, the writing on the blackboard has quite a bit of space to the right of the blackboard. As she is telling of Joseph, the second blackboard is almost right next to the first blackboard and the first blackboard doesn't have the writing on it anymore.
Continuity mistake: During Peggy's visit to Megamart she meets one of her fellow teachers when she is about to go down one of the aisles. When the shot shows Peggy talking, you can now see the aisle of products is now behind her even though she didn't move. At the end of the conversation, Peggy gives the woman a pin and the two of them have now moved again and are at the very end of the aisle that Peggy started in.
Continuity mistake: In the final classroom scene when Peggy has a mace, she swings it very hard and rips off the cartoon paper on the map of Europe. It then goes to a quick shot of the class and back to her in less than a second. Yet she is now holding the mace steady in her hand, even though you wouldn't be able to stop a mace that soon after swinging it that quickly. The cartoon paper she ripped off has also disappeared.