Nutbourn College, the most established and respectable of boys' schools, is run by unyielding Headmaster Wetherby Pond. When a military mistake billets a girls' school to share the college's premises due to wartime restrictions, he is outraged. However, he soon discovers he has met his match when he encounters the Headmistress of the girls' school in question, the formidable Muriel Whitchurch. Initially the two are hostile to one another, but with a staff of dazed, eccentric teachers and a student body whose mischief knows no bounds, they are forced to pull together. Then, just when they thought the situation couldn't get any more complicated, they discover they are faced with two troublesome visits on the same day; one from a group of parents, who must believe the school is only for girls, and one from the Ministry, who must be presented with an all boys establishment!