Continuity mistake: When Sir James and Sylvia arrive by coach at the Tompson home, the driver carries their baggage to the door. He is played by a younger actor with darker hair initially, but when the shot changes to the door of the house, he is suddenly being played by a noticeably older actor with grey hair yet wearing the same clothes and still carrying the same bags.
Factual error: The uniforms worn by the engineering force are from the wrong era. Prior to 1941 the left arm rates had the head of the eagle pointing to the wearer's rear. Steve McQueen and the rest of the Engineering force rate eagle head is pointing forward, which is from WW2.
Plot hole: All the teen girls are about the same age and always in the same grade-level during their three years at St. Francis. There are no younger new students arriving each fall, nor do older ones graduate in the spring. Every student graduates at the end of the three years. Schools do not accept a new crop of students every three years.
Continuity mistake: At the beginning, Aldo escapes at precisely 3:00. But when driving away, they pass a store-front clock which reads 12:30.
Continuity mistake: Didi is wearing a long black negligee when Pepe throws her into a bubble-filled bathtub on a movie set. When she gets out of the tub and runs off, the negligee has disappeared and she is covered only with bubbles.
Visible crew/equipment: After Matt's arrested at the discotheque, when he's at the police station with Julian, the chalk actor's mark can be seen on the floor in front of Matt's feet.
Continuity mistake: When the four kids uncouple the coach from the engine Carole is wearing trousers. The stationmaster tells them to stand clear as the engine pulls away, in the first shot of the children after the engine has gone Carole is still wearing her trousers but in the second shot Carole is now wearing a skirt.