Two unpopular queer high-school students start a fight club to have sex before graduation.
After they accidentally injure their high school's star quarterback Jeff by hitting him with a car, transforming them from awkward outcasts to overnight celebrities, best friends PJ and Josie concoct an elaborate lie about having spent time in a juvenile correction facility over the summer, and with their equally-awkward friend Hazel and teacher Mr G, they start a self-defense club for women in an attempt to lose their virginities to Brittany and Isabel, their cheerleader crushes.
Best friends PJ and Josie are unpopular lesbian virgins at football-obsessed Rockbridge Falls High School. At the back-to-school fair, they unsuccessfully flirt with their respective crushes, popular cheerleaders Brittany and Isabel. When they see Isabel arguing with her boyfriend Jeff, the school's star quarterback, PJ and Josie invite her into their car to escape. They gently bump into Jeff when he refuses to move, prompting him to feign injury in front of the entire football team.
At school, rumors spread that PJ and Josie spent the summer at juvenile detention. Threatened with expulsion for Jeff's "injury", Josie lies that they were practicing for a feminist "self-defense club" to avoid punishment. With the help of their friend Hazel, PJ and Josie actually start the club, with the ulterior motive of attracting girls. They persuade their disinterested history teacher Mr. G to serve as the club's required advisor, convincing him that the group promotes female solidarity.
PJ and Josie embrace their reputation as violent delinquents as the club attracts more members, including Brittany and Isabel, with "lessons" in self-defense that consist of the students beating each other up. The club bonds through their chaotic, bloody sessions, and PJ and Josie grow closer to Brittany and Isabel. Meanwhile, Jeff's overprotective best friend and teammate Tim confirms his suspicions that PJ and Josie never went to Julie.
Hazel discovers that her recently divorced mother is sleeping with Jeff, and Josie informs Isabel, who breaks up with Jeff in front of the entire cafeteria. While the club vandalizes Jeff's house, Josie and Isabel almost kiss before a vengeful Hazel blows up Jeff's car with a homemade bomb. Tim warns Josie to end the club, but the members decide to disband before they can be punished for the explosion, and a frustrated PJ lashes out at Hazel. Josie and Isabel have sex, while PJ kisses Brittany, but is disappointed to learn she is straight.
At a pep rally for the school's upcoming football game against longtime rival Huntington High, Tim tricks Hazel into representing the club by fighting the school's top boxer. Despite showing off some of her newly acquired skills, Hazel is badly beaten, as Tim exposes PJ and Josie's lies and their original selfish reasons for founding the club. Isabel turns against Josie, who falls out with PJ, and they are told off by Mr. G, who renounces feminism. The feuding friends are further ostracized at school, while Jeff wins back Isabel.
Josie seeks advice from her and PJ's childhood babysitter Rhodes, who reveals that Huntington tradition involves killing a Rockbridge football player. Josie and PJ reconcile with each other and with Hazel, reuniting the club in an effort to stop Huntington's plans. At the game, they discover pineapple juice has been added to the football field's sprinkler system to kill Jeff, who is deathly allergic to pineapple.
Hazel attempts to distract the crowd with another bomb, which fails to detonate, leading her and PJ to divert attention by making out. Isabel and Brittany rejoin the club in a brutal brawl with the Huntington team, as Josie carries Jeff to safety before the sprinklers go off. With most of the Huntington players dead, Tim realizes the plot to kill Jeff and leads the crowd in celebrating the club for saving him. Josie and Isabel embrace with a kiss, while Hazel's bomb finally explodes.
