College sophomore Elizabeth Wolff (left) and her former Brearley classmates have graduated from the official school uniform. Now the strict dress code they follow is self-regulated.Photo: Kai Wiechmann

Before we finished our senior year, my friends and I looked around our intimate calculus class and counted six pairs of Seven jeans, six pairs of gray New Balance kicks, six hooded Brearley sweatshirts. How had the truth escaped us for so long? “Oh, my,” said my friend Sam one day after a sudden realization—“we’re clones.”

Of course, since we were 5 years old, my friends and I have been wearing identical clothes—only then they were uniforms in the official sense. On the 79th Street crosstown bus, I could always spot my allies by their blue tunics and my rivals by their lime-green Chapin jumpers. This was how we quickly learned who was one of us and who wasn’t: by our clothes.

Once we were allowed to go outside by ourselves in middle school, and out at night in high school, we were inventing our own occasion-specific (and intelligence- and wealth-specific) uniforms. And when our school considered us old enough to dress ourselves (at Brearley, we stopped wearing uniforms after eighth grade), we realized what hard work it can be to put together an outfit that sends the right message every single day. By employing certain fashion and shopping strategies, you let everybody know (or at least everybody who knows know) that you are (a) from Manhattan, (b) from a posh school in Manhattan, (c) aware that they’re sizing you up (and you are sizing them up), and (d) a social ally, competitiveness notwithstanding. It’s tribal fashion.

The wardrobe is also a pavement thing. In suburbia, stilettos sink into sod and morning dew does a number on suede. My suburban counterpart—I’ve learned at college—is preoccupied with how to get herself from point A to point B, so the vehicle becomes the statement; the city girl is concerned with how to carry her stuff from A to B, so it becomes about the bag and the shoes. When I first bought a car my freshman year, I asked my friends for a translation from “car” to “clothes.” I settled on Volkswagen: the Gap of the automotive world.

By 13, city girls have already learned how to identify Petit Bateau T-shirts from the light of a movie screen. By 18, we’ve trained our eyes to spot Alvin Valley pants (hip-hugging, three-inch, belt-like clasp), Vanessa Bruno blouses (thin fabric), and Catherine Malandrino skirts (they swirl). Brand-smart eyes were second nature; I walked to school and clocked the blocks with handbags—Gucci Gs, Prada triangles, Marc Jacobs clasps.

Now I look at the connotations of brands, prices, and cuts like a complex politics, and I’ve become an expert. The important Kremlinology begins in the stores. My friends and I go to the boutiques most often: Scoop, Searle, Intermix, Big Drop, and, in the summer, Calypso. We start at the front, which tends to be split by price and degree of formality. One side will be noticeably more expensive and fanciful than the other. The cheaper section (which is, by any standard, not cheap) may mix in button-down shirts and hooded sweaters with sexy, suggestive tops. The more expensive side always seems to dabble in layers. In the middle of the store are belts and denim.

Sometimes my friends and I shop at Barneys—but that’s where you get into the financial distinctions that are better to avoid: Were both friends eighth-floor shoppers, or could one shop on seven—or even six?

Shopping at its best is about moving ahead, making a new statement about yourself—but it’s just as much about not falling behind.

In my world, here’s the basis of any social survivor’s wardrobe:

Jeans: Sevens, Citizens of Humanity, a Diesel pair: They’re your generic high-end pants and look good only on the very thin.

Coats: One North Face shell, one black cashmere or cashmere-wool-blend single-breasted coat. Acceptable brands are Barneys private label (cheapest), Searle (middle of the road), and runway brands (much, much more).

Shoes: Must be positively recognizable. Tod’s loafers, Prada heels, leather stiletto boots, Reef flip-flops, and an unassuming sneaker like a Puma or a New Balance.

Tops: Lacoste shirts are boring but get the job done. More than one cashmere sweater is a requirement—it’s the thinnest material you can wear in the dead of winter. A small drawer of Hanes three-for-$9 ribbed white tank tops. Somewhere along the way, they became sexy (according to girls) for girls to wear.

Bags: Every private-school girl sizes up her handbag against the others in any given room. Expensive is the point. But if you aren’t fortunate enough to be able to afford the latest Chloé bag, you work harder to find a purse that can withstand the scrutiny. You find something unique, even inexpensive, and call it “vintage.” “Vintage” is the social survivor’s fig leaf.

If you’re missing any of these components, rebellion is a useful fashion strategy—become “morally opposed.” “The North Face is a name-brand gimmick,” I decree when I show up at school with a Patagonia version. “Dyeing your hair when you’re 16 is disgusting,” I sneer, as if it had been my choice, rather than my mother’s insistence, that I keep my natural color. “Aren’t you fancy?” I jibe, so I can make my jeans and hooded Juicy sweatshirt seem like the assigned uniform for the occasion when, in fact, I’m underdressed.

When we do, finally, leave the city, we discover that college is, in many ways, the end of fashion, or at least it’s reverse fashion. My college has clothing-optional dorms. I give in to Birkenstocks (because that’s the uniform), but I can’t quite seem to shake my excitement when I discover a Barneys outlet on I-95.

But I go alone.