In the Story "A&P" by John Updike, what is the theme being expressed throughout the story?

The main theme that runs through A & P is the idea of choices and consequences. There is also a commentary in the story about freedom and rules.  Sammy works at a supermarket where he views all the people he sees as stupid sheep.  He observes the activity in the store from a sarcastic, mocking tone.  Everyone looks the same to Sammy except when the young girls come in wearing the bathing suits.  

"A few house-slaves in pin curlers even looked around after pushing their carts past to make sure what they had seen was correct." (Updike) 

Sammy is young, 19, and very bored with his job at the store. His interest is peaked, however, when 

"In walks these three girls in nothing but bathing suits. I'm in the third check-out slot, with my back to the door, so I don't see them until they're over by the bread." (Updike)

Sammy is infatuated, immediately with the three girls, particularly one he names Queenie.  Sammy contrasts the three scantily clad girls with the usual shoppers in the store.

Sammy gets so interested in the girls that when the store manager, Lengel scolds them for being improperly dressed to shop, he abruptly announces that he quits.

Sammy's actions are a reaction to the girls being told they were inappropriately dressed for shopping in the store, he does not think about the consequences of his actions.  He is only thinking about being on the side of the three girls who he sees as heroes for exerting their rights as individuals and violating the rules of the store.  He especially likes the fact that the girls shock the regular customers out of their zombie like shopping.  

This story is set in the 1960s, so girls were usually dressed appropriately, even down to white gloves sometimes.  So it is very unexpected to see three girls in bathing suits in the supermarket.  

Sammy links himself with the three rebels and is desperate to get their attention, however, they walk out of the store without giving him a second look.  So as he leaves the store, now jobless, he discovers that he has made his life a lot harder with his impulsive behavior.

Choices, that is what Sammy makes when he quits, have consequences.  Freedom of one individual should not impose on the freedom of another.  The improperly dressed girls violated the rules of the store by shoping in their bathing suits thereby violating the rights of the other shoppers by making them uncomfortable in the environment.

Rebellion is also a theme that is relevant to this story, the girls obviously don't care that they are wearing bathing suits in a store, they are not embarrassed, they don't care.

Sammy's actions at the end of the story are the ultimate rebellion, a take this job and shove it mentality which only feels good when you say it, then you realize that you have no job, no money and big problems.