In the stereotypical high school community of John Hughes High in Southern California, attractive Priscilla (Jaime Pressly), a popular cheerleader, separates from her talented football star but slacker boyfriend, Jake Wyler (Chris Evans). After Jake discovers that Priscilla is now dating timid and weird Les (Riley Smith) just to spite him, one of Jake's friends, Austin (Eric Christian Olsen), makes a bet with him to turn Janey Briggs (Chyler Leigh), a "uniquely rebellious girl", into the prom queen.

Jake attempts to court Janey's love, but faces adversity from his own sister, Catherine (Mia Kirshner), who is sexually attracted to him; Janey's unnoticed admirer and best friend, Ricky Lipman (Eric Jungmann); and memories from his past football career. Catherine eventually assists her brother by "drastically" altering Janey's appearance (which is simply removing her glasses and ponytail), instantly making her drop dead gorgeous.

Meanwhile, Janey's younger brother, Mitch (Cody McMains), and his friends Ox (Sam Huntington) and Bruce (Samm Levine), make a pact to lose their virginity by graduation despite still being in their freshman year. Mitch tries to impress his longtime crush, the beautiful yet perverted Amanda Becker (Lacey Chabert) with a love letter. Bruce says that he does not have a chance with her, mockingly stating, "Keep dreaming!"

As the prom draws near, Jake draws infamy among his peers after he fails to lead his football team to victory at the state championship game the year before. The situation is further worsened when Austin tricks Jake into telling Janey about his bet to spite Priscilla by pretending to whisper the secret bet in Janey's ear, causing her to immediately leave Jake in anger. During prom night, Austin and Janey go together; a jealous Jake and Catherine have a dance-off with Austin and Janey, with Catherine dancing in a sexual manner. Janey runs off crying. Meanwhile, Mitch and his friends are having a lousy time at the prom until Amanda arrives and Mitch gives her the letter (to which she responds that she does not have sex with every loser who does such, but will give them handjobs), horny Bruce hooks up with the equally horny international student Areola (Cerina Vincent), and Ox later hooks up with Catherine after sharing a romantic and rather odd connection.

Jake is awarded prom king and the principal reads out that the votes for prom queen are tied. Everyone thinks that it is between Janey and Priscilla, but they are shocked to find that Kara (Samaire Armstrong) and Sara Fratelli (Nectar Rose), conjoined twins, win prom queen. During the traditional prom king and queen dance, Janey supposedly left with Austin to go to a hotel.

Jake goes to the hotel room where he finds Austin having wild sex with a girl, but is shocked to find that it is Priscilla and not Janey, while Les videotapes them with his pants down. Austin tells Jake that Janey "ran home to her daddy". Jake coldly punches Austin and Priscilla, knocking them unconscious for their part in Janey's humiliation. He then punches Les for "being really weird" (he also punches a plastic bag that happens to be floating next to Les); afterwards he runs to Janey's house only to learn from her father that she is going to Paris for art school.

Jake arrives at the airport and confronts her before she can board the plane, but uses a plethora of clichéd lines from other films (such as She's All That, Cruel Intentions, American Pie, The Breakfast Club, American Beauty, 10 Things I Hate About You, Can't Hardly Wait, and Pretty in Pink) to convince her to stay home in America. His final (and only original) speech suggests they would be better off separated, but Janey mistakenly believes he is quoting The Karate Kid, and she decides to stay with him.

In a mid-credits scene, Janey's father Mr. Briggs (Randy Quaid) drunkenly assaults himself with pies in his kitchen. In a post-credits scene, an earlier seen Albino Folk Singer (Joy Gohring), an afroed student with a guitar, reveals that she has become blind and calls out for assistance upon completing her song, while an audience member calls for another to assist in stealing her guitar.