While Bart and his classmates are on a field trip to the Springfield Police Station, Bart sneaks away and discovers a large quantity of bullhorns. Grouping them together, he speaks into the powerful, single mega-bullhorn. A soundwave explosion rocks all of Springfield, shattering windows and temporarily deafening the populace. As punishment, Homer and Marge enroll Bart in a military academy.

After surveying the academy, Lisa decides that she, too, would like to enroll. However, the facility has never had a female cadet and the academy’s commandant is taken aback. Nevertheless, he relocates a group of cadets, giving Lisa her own barracks. The move creates a wave of resentment and hazing activities. Even Bart refuses to speak to his sister.

Later, Bart secretly apologizes to Lisa and asks her to remain at the academy. .Lisa is convinced that she will not pass a test in which the cadets must traverse a 150-foot rope over thornbushes. Bart covertly trains her but publicly continues the silent treatment. Lisa begins to climb, but stops halfway across, exhausted. Bart breaks with his classmates and shouts words of encouragement to her. Her spirits lifted, Lisa continues the climb and passes the test.