Cadet Gary McKeever wants to join his father, an U.S. Air Force major, who is stationed in Paris. Currently enrolled in a stateside military school, he schemes to be kicked out by amassing demerit and demerit. The school's headmaster, Colonel Blackwell, knows that Gary's leadership score is off the charts and refuses to dismiss him.
McKeever misinterprets a letter from Tubby's parents and thinks they will withdraw him from the academy because of financial difficulties. The boys decide to raise money but their use of school supplies to do so makes the Colonel suspicious.
McKeever is assigned to write the school play honoring Blackwell, an ancestor of the Colonel. When Blackwell's army record reveals he was not a hero, McKeever doesn't know how to avoid upsetting the Colonel with the news.
In an attempt to improve discipline at the Academy, the Colonel brings in Sergeant Max Gruber, unaware she is a woman. She proves to be too strict and it is up to McKeever and his friends to soften her up.
When Andrea overhears her uncle, Colonel Blackwell, tell his aide to keep her from meeting Gary McKeever, the rebellious child tries to spend ever waking minute with the cadet. She even convinces him to play a prank on her uncle which backfires badly.