TONY: Everything's important, Riff. You, me, the sweet guy I work for. […] I promised Doc I'd clean up the store tonight.
When Riff tries to convince Tony to come to the dance to confront the Sharks, he resists. We see him cheerfully hauling around cases of soda at Doc's store and generally being a good guy. He's done with the Jets; other things are more important to him now. He's become a hardworking guy; it's a hopeful picture. Does the movie's ending prove there's really no escape from your social circumstances no matter how hard you try?
MARIA: If Bernardo knew.
TONY: We'll let him know. I'm not one of 'em, Maria.
MARIA: But you are not one of us. And I am not one of you
Racial conflict divides people into "us" and "them," and this never ends well. Tony's the romantic who thinks that their love will transcend that. Maria's more practical, probably because as an immigrant, she's been on the receiving end of racist attitudes.
RIFF: Dear kindly Sergeant Krupke, Ya gotta understand-- It's just our bringin' upke That gets us outta hand. Our mothers all are junkies, Our fathers all are drunks. Golly Moses, naturally we're punks!
Although this is a comic piece, it shows us that Riff knows a lot about the causes of juvenile delinquency—or at least what the generally accepted theories are. Naturally, the Jets are singing it to each other because the people in a position to do something about it (like Sgt. Krupke himself) really just don't care.
A-RAB: Officer Krupke, you've done it again. This boy don't need a job, He needs a year in the pen! It ain't just a question of misunderstood; Deep down inside him, he's no good!
RIFF: I'm no good!
JETS: We're no good, we're no good, We're no earthly good, Like the best of us is no damn good!
The song ends with the Jets confirming all of the class prejudices levels against them. Kind of a bummer for such a funny and upbeat song, but it shows that Riff knows the score.
SCHRANK: Now look, fellas. Let's be reasonable. If I don't get a little law and order around here, I get busted down to a traffic corner. And your friend don't like traffic corners. So that means you're gonna start making nice with the PRs from now on. I said nice, get it? Because if you don't, and I catch any of you doing any more brawlin' in my territory, I'm gonna personally beat the living crud out of each and every one of you and see that you go to the can and rot there.
Schrank is the film's representative of the class in power. We're guessing he himself isn't much higher in the social pecking order than the Jets and the Sharks and he knows it could get worse. That gives him the motivation to keep them in line, or throw them in jail or even shoot them if the circumstances are right.
SCHRANK: All right, wise guys. Now you listen to me. All of ya! You hoodlums don't own these streets. And I've had all the roughhouse I'm gonna put up with around here! You wanna kill each other, kill each other! But you ain't gonna do it on my beat. Are there any questions?
BERNARDO: Yes, sir. Would you mind translating that into Spanish?
Again, the Jets and the Sharks can't do much about Schrank, and the higher classes he represents. The best they can manage is giving him a hard time. It's not much, as acts of defiance goes, but it's really all they've got.
SCHRANK: Oh, I know. It's a free country and I ain't got the right. But I got a badge. What have you got?
At the end of the day, Schrank just dispenses with the pretense and gives them the truth: he has the power to do what he wants to them and he can exercise it just because. This is an admission that brute force is all he needs, not any kind of justifiable reason.
ICE: You wanna live in this lousy world? You play it cool
Hard to argue with his logic. Things are tough all over, and raging about it is only going to turn around and bite you. The only way the Jets can avoid being pounded by their social "betters" is to stay calm, keep it together and take revenge when the cops aren't looking.
MARIA: Stay with me. Don't leave me...hold me...tighter.
TONY: It'll be all right, I know it. We're really together now.
MARIA: But it's not us. It's everything around us.
TONY: Then I'll take you away where nothing can get to us, not anyone or anything.
People in the underclass, or who are struggling financially often express the need to leave wherever they're at: to move out of their neighborhood or otherwise escape. It's hard to do it you don't have any opportunities, which may be why these two are ultimately doomed.
SCHRANK: Why don't you get smart, you stupid hooligans? I oughta take you down to the station and throw you in the can right now. You and the tin-horn immigrant scum you come from.
Again, stay classy, lieutenant. But he has a way of cutting through the phoniness and the bull and reminding the gang members of exactly how much power they don't have.