When the teachers' union reaches a dead end in its negotiations with Principal Skinner, the teachers strike, forcing the Board of Education to come up with a creative way to keep the school running. The only plan that's in place is to have highly intelligent robots teach classes, but since such robots don't exist, the Board enlists PTA members for the task. With Ned Flanders as Principal and Marge as a teacher, the school functions normally, for a time. Bart realizes that without his old teachers, school just doesn't work for him, so he devises a way to bring the teachers' union and Principal Skinner back to the negotiating table: He locks Mrs. Krabappel and Skinner in a room together until they can agree on the contract.