Springfield Elementary takes an career aptitude test. The test says that Bart will be a policemen and Lisa would be a homemaker like Marge. Dismayed, Lisa turns into a naughty kid, hanging out in the bad girls bathroom.
Meanwhile, Bart goes for a ride in a police car, and helps apprehend a thief. Enjoying his new taste of authority, Bart takes sides with Principal Skinner and helps him restore order around the school.
After getting detention, Lisa steals all the Teacher's Edition textbooks to see how the teachers would do without them. Bart and Skinner search the school lockers for the lost text books. They find them in Lisa's locker, but Bart takes the blame, realizing that Lisa has more to live for. Bart is sentenced to 600 days of detention.