Cosi in Bryn Mawr, 8:07 p.m., Friday night. The woman curled in the corner with her laptop is finally giving up. She snaps it shut, slings her bag over her shoulder and leaves. She’ll remember not to come on Friday nights anymore; at least, not if she’s seeking peace and quiet. She is in her mid-30s, and it’s possible that she’s forgotten what a Friday meant in middle school.

Simply put, it was your best shot at a social life. By the time the last bell rang, you’d have sorted through the rumors and determined the where, the what, the who. The where being the location you’d ask your dad to drop you a block away from, the what being your outfit, and the who being the desirable who had casually mentioned that he or she “might stop by,” according to your best friend’s sister’s lab partner.

This evening, it seems that the teenyboppers of the Bryn Mawr area have successfully pulled off the fantasy Friday night: like, everyone is here at Cosi. There are no fewer than 50 youngsters packing the tables, walkways and sidewalk, and while a few actually glance over the menus, most are too busy concentrating on looking cool to sit down and eat.

It’s a scene both typical and startling. Literally every kid in the place wields a cell phone. The ensembles at which they tug self-consciously are invariably the handiwork of Miss Sixty and Armani. While the staff of Cosi seems to regard the adolescents underfoot as a torturous, but familiar presence, it is undeniable that the chattering group is a sampling from a brand new, brand-driven breed.

Admittedly, the young people f the affluent Villanova area may represent the biggest spenders of their age group, but today’s 12 to 20 year-olds have more purchasing power than ever. In fact, ABC News reported last year that Americans in that age bracket influence $520 billion dollars of spending each year. Their economic prowess is redefining the adolescent lifestyle.

The trend is recent but not this-minute new. Parents have caught on to their kids’ sudden attention to style; advertisers have seized the opportunity to market posh to the preteens; kids have discovered that it’s costing more and more to fit in. What’s more striking than the established presence of children as powerful shoppers is the development a key force driving their spending: the nascent social structure of child celebrities.

The lives of today’s pint-sized television, movie and music novelties bear little resemblance to those of Drew Barrymore or Michael Jackson during their child star days. Now, they multitask from motion picture to music video in the blink of an eye, run million-dollar corporations, and show up on the cover of Vanity Fair.

Mary-Kate and Ashley Olsen, who made their debut sharing the role of Michelle on the family sitcom “Full House,” have blossomed into the undisputed princesses of youth culture. Besides starring in dozens of television and video-release movies, the twins have built a formidable business on little more than their own good name – the Mary-Kate and Ashley brand covers everything from eyeglass frames to lingerie. In the past six months, rising star Hillary Duff released her first full album and starred in a blockbuster film based on the show that made her famous, the Disney Channel’s “Lizzie McGuire.” In short, being a child star (neither the Olsens nor Duff are anywhere near their 18th birthday) is no longer a stint. It’s a full-blown career, complete with the exhausting hours and luscious perks that accompany enormous success.

Those perks include red carpet events, personal stylists and innumerable designer outfits. In Vanity Fair’s July spread of the hottest teen idols, the Olsens, Duff, and the rest of the girls were polled on how many Juicy Couture velour outfits they owned. Some reported having two dozen in their closets; the sets can cost up to $200.

Dropping that kind of money for a hoodie and sweatpants is no big deal to a mini-millionaire. But even after decades of hard work, most American parents have not come close to matching the kind of money the Olsen twins make in a year. For them, it is a far more weighty decision they make when they plunk down the cash for a $198 Marc Jacobs clutch.

The prices of many of these objects of lust border on absurdity, but the most disturbing thing about the teen fashion craze has little to do with money. Far more disappointing is the fact that people are learning earlier and earlier in their lives to base their cravings on the arbitrary preferences of the elite.

As long as kids wheedle and parents concede, any adolescent can score a pair of the same jeans Duff wears and, more importantly, the sense of being just a little closer to that impossible standard of celebrity cool. But there is always someone who has more, and it’s a shame the competition can’t wait for just a few more years. For while someday these children may regret skipping $5 school dances to save for a Coach bucket hat, it is the materialistic blindness they cheated themselves of that they will miss the most.