Henry Aldrich, the teenage troublemaker of Centerville, is humiliated when no one believes his claim that he can fly a plane. On the last day for student president nominations, nominee Irwin Barrett, a smug, wealthy boy, gets two of his friends to nominate Henry in order to split the votes against him and his opponent, Phyllis Michael, who has a crush on Henry. As part of Irwin's plan, his flirtatious blonde girl friend, Geraldine Adams, promises Henry that she will go steady with him if he becomes student president. Henry is flabbergasted by Geraldine's promise and takes his nomination seriously, appointing his friend, Dizzy Stevens, to be his campaign manager. Henry pleads with his older friend, Ed Calkins, an unlicensed and unemployed transport pilot, to admit to their flying lessons so that his credibility will be restored. Ed refuses because he is afraid it might damage his chances of getting reinstated if anyone finds out that he is teaching a minor to fly an unlicensed plane. Henry's spirits sag when his family urges him to resign so that he will not embarrass himself, but he is bolstered by the support of Phyllis, who drops out of the race so that he will have a better chance. Phyllis sways other students to believe in Henry when she makes an impassioned speech against Irwin, who is bribing them with free sodas and entertainment at the soda shop. Henry has difficulty coming up with a speech until Dizzy overhears their teacher, Mr. Crosley, rehearsing his own high school speech with Irwin. Dizzy writes the speech down and gives it to Henry, and both Crosley and Irwin are appalled when they hear him speaking their words. The speech wins the students over and Crosley is unable to accuse Henry of theft without compromising himself. However, Phyllis has lost faith in Henry because she believes he stole his speech. Henry wins the election but his excitement is short-lived because the principal has evidence that the ballot boxes were stuffed, and Henry is accused of the crime. Although Henry is innocent, Crosley brings up the stolen speech, and Henry loyally refuses to name Dizzy as his cohort. Henry is expelled from school and his parents, who believe he is guilty, arrange for him to live at his uncle's home in another school district. Before Henry leaves, however, Dizzy and Phyllis come over and tell him that they suspect Irwin of making the fake ballots. The three friends learn that the printer who made the ballots has gone to Bloomingdale for a county fair. Ed flies Henry to Bloomingdale where McCloskey, the printer, agrees to return with them to Centerville and identify the culprit. A flight inspector prevents Ed from taking off because he is unlicensed so Henry, desperate, takes off suddenly. The passenger door is ripped off the plane and McCloskey experiences a terrifying flight with Henry at the controls. Ed and the inspector call the Centerville police and fire department to warn them of Henry's arrival, and they all gather at the high school. Henry crash lands the plane onto the football field and he and McCloskey emerge unscathed. McCloskey identifies Irwin as the person who bought the ballot forms and the principal makes a public apology to Henry and thereby restores his honor.
