The mischievous schoolgirls hope to get rich quick by betting on a racehorse belonging to a wealthy classmate's father. However, they first have to foil a gang of thieves planning to steal the animal and outwit an undercover policewoman sent to infiltrate the school disguised as a teacher. Comedy based on the late Ronald Searle's cartoons, starring Alastair Sim, Joyce Grenfell and George Cole.