The movie is set at St. Francis Academy, a fictional all-girls Catholic Church boarding school in Pennsylvania, operated by an order of nuns. Rosalind Russell plays the Mother Superior, who spends the movie at odds with Mary Clancy (Hayley Mills), a rebellious teenager, and her friend Rachel Devery (June Harding). The episodic story line follows the young women through their sophomore, junior and senior high-school years as they pull pranks on the sisters and repeatedly get into trouble. Although Mary spends much of her time at St. Francis resenting the authority of the Mother Superior and puzzling over why any woman would choose the life of a nun, as time goes on she is touched by examples of the sisters' dedication, devotion, kindness, love, and generosity, and begins to see that their life is one of fulfillment, not deprivation. Mary receives "Calling (religious)" senior year and, after graduation, remains at the school to begin her novitiate in the order.