In Miss Hinklefink's music appreciation class at Whitney High School, student Lee Watson complains about the illogical plots of operas. Later, when Miss Hinklefink is called away for a few minutes, Harry "The Hipster" teaches the class about meter by demonstrating a swing beat. Lee, who is always in trouble, is in the office of the school principal, Professor Owen Townley, when businessman Mr. Forrest interrupts their conversation. Forrest promises to provide the football team with new uniforms and gear on the condition that his son Jimmy is elected as student body president. Townley turns him down, but when Freddie Trimball, Jimmy's opponent, learns of Forrest's proposal from Lee, he drops out of the race. At the teen canteen, where Freddie is rehearsing a student show for the junior prom, Jimmy asks Dodie Rogers, Freddie's girl friend, to be his date for prom. When she declines, he reminds her that he will be student body president, which so angers Freddie that he decides to run against Jimmy after all. Lee signs on as his campaign manager, aided by Dodie and her sister Addie. Roy Dunn, Jimmy's campaign manager, then flatters Dodie's other sister, Betty, the editor of the school paper, who believes that boys do not find her attractive because she wears glasses. When Betty's sisters accuse her of taking the wrong side, she insists that she is objective, but adds that she does not think Freddie can be president and run the school show at the same time. The bitter campaign that ensues causes a rift between the sisters, to the dismay of their visiting wealthy uncle Daniel. As Jimmy becomes more popular, thanks to the speeches that Betty writes, Freddie prepares to concede the election. Then Lee suggests that Freddie use his entertainment talents to win. By offering to give Betty her new sweater, Dodie enlists her help. The teenagers then rent a truck and fill it with their friends, all singing a catchy tune. The election finally takes place, with the results to be announced at the prom. Because Roy is angry at Betty for appearing with Freddie, he does not ask her to the prom. Dodie and Addie feel responsible for their sister's situation and are about to insist that Freddie and Lee take them home, when Betty arrives with an apologetic Roy. Happy that the sisters are now reconciled, Daniel gives the girls' mother the deed to a new house. The gang puts on their number to great acclaim, and Freddie is declared the winner of the election. Forrest admits he was wrong and agrees to give the school new football uniforms anyway. Afterward, Jimmy and Freddie end their rivalry.
