A chauvinistic remark from Principal Skinner to a former female student results in his demotion and the school being split between the sexes. Lisa is soon fed up with the new principal's coddling style towards girls and impersonates a boy in order to learn serious math under Professor Frink. After quickly being beaten up by Nelson, Lisa seeks Bart's guidance and becomes the coolest boy in school. She ends the charade after taking high marks in math only to realize that she lost herself in the manly tactics she used to achieve her goal.