Teacher's Edition is a series of books for teachers. There are book for every subject with an answer key.
Lisa once stole all Teacher's Editions at Springfield Elementary and hid them in her locker. The teachers were helpless without them, so Principal Skinner and Bart were searching lockers. When Bart opened Lisa's one, she confessed herself and started crying. Skinner then arrived and saw that all the books had been found. He asked who the culprit was. Lisa wanted to tell him, but Bart took the fall.