“Some of you may discover a wonderful vocation you'd never even imagined. Others may find out life isn't fair, in spite of your Masters from Bryn Mawr, you might end up a glorified babysitter to a bunch of dead-eyed fourth graders while your husband runs naked on a beach with your marriage counselor!”
After taking the Career Aptitude Normalization Test, or CANT test, Lisa finds out she's more suited to be a homemaker, while Bart is more suited to be a police officer. While Bart enjoys his taste of authority, Lisa turns rebellious after being unable to pursue the career she originally wanted.
After taking career aptitude tests, scored by a malfunctioning computer, Lisa discovers that the occupation she is best suited for is homemaker, while Bart's test show that he should be a policeman. Lisa is heartbroken over the result and is determined to prove the test wrong. She consults a music teacher for his opinion, but he tells her that, having inherited her father's stubby fingers, she can never be a professional saxophone player. Lisa is therefore required by the test to spend the day doing chores with her mother Marge, while Bart goes on a ride-along with the police.
Lisa hates her role as a homemaker, and realizing that her future dreams have been shattered, she loses interest in being a good student. Marge tries to comfort her by telling her that being a homemaker isn't so bad as she can be creative in making breakfasts, like making smiley face meals for Bart and Homer, which neither of them appreciate, sinking Lisa's spirit even lower. Without any motivation to do her best, Lisa quits playing saxophone and doing her schoolwork. Bart enjoys spending time with the police, and he even ends up stopping Snake during a car chase.
When Principal Skinner discovers Bart's new interest in law enforcement— as seen in the arrest of Groundskeeper Willie for burning leaves in violation of the town's clean air laws—he enlists him as a hall monitor. He soon becomes a good student with good grades, whereas Lisa adopts a sulky, rebellious attitude. She hangs out with rebellious girls in the bad girl's bathroom, makes snippy comments to Miss Hoover by telling her to shove it, gets sent to Skinner's office for disciplinary actions and her grades drop as a result. Bart starts handing out demerits to his classmates for minor infractions and has order restored to the school. While serving detention for another nasty comment towards Miss Hoover, Lisa secretly steals all of the Teachers' Editions of the schoolbooks and reveals the teachers' lack of education. It's up to Bart to figure out who stole the books. Realizing Lisa is the culprit, Bart takes the blame as he knew that Lisa has the brain to do whatever she wants and he'll "be there to borrow money" and returns to his life as a bad student and detention regular. Lisa, touched by Bart's actions, goes back to being a good student and playing the saxophone. As Bart spends his time in detention, Lisa plays her saxophone outside his classroom to comfort him while Bart encourages her.