Dress standards on U.S. campuses aren't what they used to be. Undergrads from Peoria to Princeton attend lectures in slouchy jeans and flip-flops; in the "The Social Network," David Fincher's film about the birth of Facebook, Mark Zuckerberg (played by Jesse Eisenberg) claws his way to the top at Harvard wearing loose-fitting hoodies.

According to Christian Chensvold, founder of the highbrow fashion website Ivy Style, most of today's elite college students are "taking their style cues from the bottom of society, not the top."

Photos: Give It the 'Ol College Try

Funnily enough, a sizable part of the fashion industry is doing just the opposite, turning out updated versions of the clothes worn by the modern undergrad's privileged predecessors. The so-called Ivy League Look—with its signature chinos, oxford button-downs, soft-shouldered jackets and crew-neck letterman sweaters—is back in a big way. And if it succeeds in trickling down to the youth market, campus style may even start to resemble what it used to be.

A casual uniform that peaked in the mid-'60s, just before co-ed campuses and the hippie movement, the Ivy League Look isn't exactly a fresh point of reference. What's new about this latest interpretation, though, is that it's less fanciful—instead of a Wes Anderson character in a skinny tweed suit, it evokes an approachable guy who doesn't mind scuffing his khakis playing football.

"Ivy League style was something that just was, as opposed to something intended to create an effect," said David Wilder, a veteran sales associate at J. Press in New York. (According to the company's website, the brand has been "dressing men to the Ivy League standard since 1902.") At least it was for anyone who was the real deal—in other words, "old-money guys who'd all gone to prep school, had that natural nonchalance, and looked like they'd been living in their clothes since the day they were born," Mr. Chensvold said.

That species is the revered subject of "Take Ivy," an influential study of elite Northeastern campuses published in 1965 by a team of fashion-savvy Japanese writers and photographers. For years a cult item among fashion insiders, the book was finally released in U.S. stores (including the ever-trendy J. Crew) this summer, flooding the menswear world with images of wholesome-looking '60s undergrads bent over books in libraries, strolling across leafy quads and—perhaps most importantly—demonstrating a robust enthusiasm for sports. "A fragile, twiggy physique is far from the ideal image of an Ivy Leaguer," the book's authors note.

A photo from "Take Ivy." From Take Ivy by Teruyoshi Hayashida/powerHouse Books

"The jockier version is the more authentic version" of the midcentury Brown or Dartmouth man, designer Michael Bastian said. "It wasn't dandified or conscious—at the heart of it, it's just guys being guys." For all the scholarly and social cachet the term confers, the Ivy League is, strictly speaking, nothing more than an athletic conference.

Mr. Bastian has zeroed in on a sports theme in his new line for Gant. As part of the venerable Swedish-owned label's larger effort to return to its American roots, his three collections for the brand to date have been inspired by lacrosse, baseball players and New England cross-country skiers.

Once the world's largest shirt manufacturer, Gant helped define the original Ivy League Look, along with J. Press and Brooks Brothers. Lately, it has ramped up its efforts to reclaim that heritage. In November, Gant opened a store in New Haven, Conn., the company's birthplace, in the heart of the Yale campus. And in an attempt to restock its archives, the shop is inviting customers to swap their old Gant shirts for new ones.

Newer menswear labels are also pushing the collegiate look, from smaller players like Carpé to giants like Rugby Ralph Lauren. The letterman jacket has become a staple of fashion-forward labels like Band of Outsiders and Shipley & Halmos; and thanks to adopters like Prep World, a new capsule collection from Tommy Hilfiger, letter sweaters will not be hard to find in stores this year. Last year saw the reboot of Boast, a sportswear label that was founded in 1973 by former Cornell squash player Bill St. John and once outfitted many an Ivy League squash team. And Harvard itself got in on the game in 2009, when it somewhat controversially lent its name to a preppy clothing line, Harvard Yard.

A Gant ad from the 1970s

Many proponents of the Ivy trend are quick to define it against the "P" word, though. "To me, 'sportswear' is the word that should be associated with Ivy style, whereas 'preppy' is irreverent, almost quirky," said Chris Callis, a Princeton junior and co-founder of the popular website Prepidemic. And according to Mr. Cotsvold, of Ivy Style, "'Preppy' is now just a sort of throwaway term for anything that looks remotely clean-cut. It's been watered down to mean anyone who's not a delinquent."

When Mr. Cotsvold started his website in late 2008, he said, "I did not foresee that fashion companies would start using the words 'Ivy,' 'collegiate' and 'varsity' more in their marketing. But it has become clear that something very zeitgeisty is happening."

Nostalgia plays no small part in it. Thanks in large part to "The Official Preppy Handbook," which archly defined the style three decades ago, "preppy" is often associated with a smirking sense of self-awareness. (Authors Lisa Birnbach and Chip Kidd released a follow-up, "True Prep," last September.) The less flamboyant Ivy look, on the other hand, emerged from what is remembered as an optimistic, postwar age of innocence. "America was the cool teenager that everyone wanted to be," Mr. Bastian said. "It's the classic American hero: well-rounded and approachable, happy and healthy. If he's beautiful, he doesn't know it."

Of course, he was also the product of a college admissions system that most would argue has changed for the better in the wake of the civil rights and women's movements. For all the emphasis on sports in the all-male era, it's difficult not to conclude that the overall vibe on Ivy League campuses 50 years ago was less competitive. "I think it's harder to be the total package now, because we live in a time where to make yourself economically valuable you have to specialize," said Prepidemic co-founder Woody Hines, who theorizes that he might not have been accepted at Princeton had he quit track during his senior year of high school.

Tennis Racquet F. Martin Ramin for The Wall Street Journal, Styling by Sharon Ryan & Anne Cardenas

Mr. Callis, one of just a few Americans on the Princeton squash team, suggests that rowers (many of whom still hail from Northeast boarding schools) are the only athletes on campus who dress anything like the sportsmen of the "Take Ivy" era. "Look at the football, basketball and baseball guys at Princeton and I don't think you'd see a style that's much different than you would at Ohio State," Mr. Callis said.

That may change as the resurgent collegiate look makes inroads on Northeastern campuses. Few brands have targeted university students as aggressively as U.K. clothing company Jack Wills, which opened an American flagship store this fall in Boston. The 11-year-old brand draws heavily on the sporting traditions of the British elite, with contemporary cricket jumpers, rugby shirts and striped blazers inspired by Oxbridge rowing clubs.

"There's an amazing history there, and these things are still relevant to kids today," said Sarah Holme, the brand's creative director. Last summer, they opened shops and threw parties in Nantucket and Martha's Vineyard; since 2008, they have hosted Yale and Harvard's teams at an annual polo match it sponsors in the U.K.

Gant, too, is banking on renewed interest among undergrads. In addition to opening the New Haven store, the brand is releasing an oxford button-down created in collaboration with the now-defunct Yale Co-Op label in February. "You think maybe it will attract the guys who remember the Co-Op, but we've had a lot of inquiries from students," Gant USA president and CEO Ari Hoffman said.

No word on whether those Yalies will sandpaper their collars for a more worn-in look, as new-money students desperate to fit in at Princeton did a half-century ago. "Even during the heyday of the Ivy look, you still had to get it right," Mr. Cotsvold said. "I don't think they were any less self-conscious than we are now."