A&P is also the name of a short story collection by John Updike first published in 1962, it contains the story of the title.
Although they are dressed for the beach, Sammy allows the girls to continue shopping while he appraises them sexually in the manner of teenage boys. He imagines for himself details of the girls from their appearance alone, undue impressions that, to his surprise, are shaken when the leader of the trio, a stunning girl he has dubbed "Queenie", speaks in a voice unlike that which he had created in his mind. Lengel, the old and prudish manager, feels that the girls are not clothed appropriately to come into a grocery store. He admonishes them that this isn't the beach and that they must have their shoulders covered next time, or have their business refused, embarrassing the girls.
Sammy is offended by this mistreatment of these customers' dignity, and ceremoniously removes his store apron and bow tie and resigns on the spot, despite the mention by the manager of the pain this would cause his parents. Sammy then leaves the store, seemingly in expectation of some display of affection or appreciation from the young women involved, only to find that they've already left, apparently oblivious to his presence. Sammy's disappointment in this development strikes a very typical Updike theme.