I'm very fond of an English film from the 1950s or so called The Happiest Days of our Lives. Sadly, it doesn't seem to be on DVD.

Alistair Sim plays the headmaster of a small English boarding school for boys, and Margaret Rutherford the headmistress of a boarding school for girls.

Through some glitch at the ministry, the two schools have been moved into the same building. For various complicated reasons, they have to live with this - then a set of parents come to inspect one school on the Parents' Day of the other, and both schools have to try to conceal the other from their own set of parents.

It's very funny, with Joyce Grenfell playing a sportive sports mistress, etc.