The Trouble with Angels (movie, 1966)

Mary and her friend, Rachel, are new students at St. Francis Academy, a boarding school run by the iron fist of Mother Superior. The immature teens grow bored and begin playing pranks on both the unsuspecting nuns and their unpleasant classmates, becoming a constant thorn in Mother Superior's side. However, as the years pass, Mary and Rachel slowly mature and begin to see the nuns in a different light.