Elizabeth Halsey is an immoral, gold-digging Chicago-area middle school English teacher who curses at her students, drinks heavily, smokes marijuana, and shows movies while sleeping through class. She plans to quit teaching and marry her wealthy fianc , Mark, but when he dumps her after learning she is only after his money, Elizabeth must resume her job. She tries to win over substitute teacher Scott Delacorte, who is also wealthy because his family runs a watch company. Amy Squirrel, a dedicated but overly enthusiastic colleague, also pursues Scott while the school's gym teacher, Russell Gettis, makes it clear that he is interested in Elizabeth romantically; she, however, is not interested in him because he's just a gym teacher.
Early in the film, Elizabeth plans to get surgery to enlarge her breasts, and becomes all the more motivated to do so once she learns Scott's ex-girlfriend had large breasts. However, when she tries to schedule an appointment for her breast surgery, she cannot afford the $9,300 procedure. To make things worse, Scott admits that he has a crush on Amy, and that he only likes Elizabeth as a friend. Elizabeth attempts to raise money for the surgery by participating in her 7th grade class car wash in provocative clothing and by manipulating parents to give her money for more school supplies and tutoring, but her efforts are not enough. Amy, acting on the growing resentment between them due to Elizabeth pursuing Scott and ignoring school rules, attempts to warn the principal about Elizabeth's embezzlement scheme, but he dismisses her claims as groundless.
Elizabeth later learns from her best friend, Lynn Davies, that the teacher of the class with the highest state test scores will receive a $5,700 bonus. With this knowledge, Elizabeth decides to change her style of teaching, forcing the class to intensely read and study To Kill A Mockingbird for the upcoming test. However, the change is too late and insufficient. The students have terrible scores on their quizzes, frustrating her even more. Meanwhile, she befriends Russell the gym teacher as Amy and Scott start dating. Desperate to pay off the procedure for her breast surgery, Elizabeth steals the state test answers by disguising herself as a journalist and seducing Carl Halabi, a state official who is in charge of creating and distributing the exams. Elizabeth gets Carl drunk and convinces him to take her to his office to have sex, but she spikes his drink and steals a copy of the answers. A month later, Elizabeth's class aces the test and she wins the bonus, giving her the funds needed to get her breasts enlarged.
When Elizabeth learns that Amy and Scott are chaperoning an upcoming field trip, she smears an apple with poison ivy and leaves it for Amy, who ends up with her face breaking out in blisters, so she cannot go. On the trip, Elizabeth seduces Scott. They dry hump and Elizabeth secretly calls Amy using Scott's phone leaving a message recording all the action, ensuring she knows about the affair. However, Scott's peculiar behavior, which was subtly exposed by Russell, disappoints Elizabeth. Elizabeth later gives advice to one of her students who has an unrequited crush on the superficial Chase in class, which causes her to reflect on how she has been superficial as well. On a field trip the boy makes an embarrassing public confession of his love and is ridiculed by his classmates. Elizabeth takes him aside, gives him her bra, and tells everyone she caught him having sex with a student from another school, which erases his image as a loser.
Left behind at the school, Amy switches Elizabeth's desk with her own to trick the janitor into unlocking Elizabeth's sealed drawer. Amy finds Elizabeth's journalist disguise and the practice test, which leads her to suspect Elizabeth cheated on the state exam. Amy informs the principal and gets Carl to testify against her. However, Elizabeth took embarrassing photos of Carl while he was drugged and, with the help of her roommate, Kirk, uses them to blackmail him to say she is innocent. Having failed to nail Elizabeth for cheating, Amy accuses her of drug use, based on a tip from a student. When the police arrive and bring their sniffer dog to search the school, they find Elizabeth's mini liquor bottles, marijuana and OxyContin pills in Amy's classroom, in a secret compartment in Elizabeth's desk which Elizabeth helpfully points out to the police. At the end of the school year, Amy is moved to the worst school in the county by the superintendent. Scott asks Elizabeth to start over, indicating that he now has a crush on her, but Elizabeth rejects him in favor of a relationship with Russell, who she has learned she has a lot in common with.
When the new school year starts, Elizabeth has not gotten the breast enlargement after all, because she feels that she looks fine the way she is. She also has a new position as the school's guidance counselor.
Output: Why did Carl change his mind about testifying against Elizabeth for cheating?