Bart and his classmates tour the Springfield Police Station during a field trip. Bart gains access to a large quantity of bullhorns. He groups the devices together, forming one mega-bullhorn, then speaks. A sound wave explosion rocks all of Springfield, shattering windows and temporarily deafening the populace. As punishment, Homer and Marge force their son to enroll in a military academy. After surveying the academy, Lisa decides that she, too, would like to enlist.

The Commandant is taken aback by Lisa’s request, as the academy has never had a female cadet in its 185 year history. But he nonetheless relocates a group of male cadets, allowing Lisa to have her own barracks. The move, however, creates a wave of resentment. Cadet Larson vows to drive Lisa from the academy by subjecting her to a brutal hazing. Though both Bart and Lisa endure the hazing process, the cadets make Lisa suffer all the more. Later, the cadets subject her to a “freeze out,” in which everyone at the academy gives Lisa the silent treatment. Even Bart refuses to speak to his sister—until he finds her alone in the barracks, hugging a cassette player as Marge’s reassuring voice sings “You Are My Sunshine.”

Later, Bart apologizes to Lisa for giving her the silent treatment, and encourages her not to quit the academy. Then the Commandant announces that everyone must pass a test called “The Eliminator,” in which the cadets are required to climb across a 150 foot rope stretched across a row of bramble bushes. Lisa grows nervous, convinced she cannot make the climb. At night, Bart takes her to the Eliminator and encourages her to practice. But she loses her grip and falls into the thorn bushes below. The day of the test arrives. Bart and his classmates successfully climb across the rope. Lisa begins her crawl, but half-way across, she suddenly stops, exhausted. Bart breaks the freeze-out and encourages Lisa to continue. Her spirits lifted, Lisa completes the journey. Later, the Commandant presents her with a medal.