PACIFIC PALISADES, Calif. - It's another pristine day at Jacqueline Kennedy High School in Southern California, just a mile up the hill from Pacific Coast Highway. Out on the large, oval-shaped quad, kids are tossing a football, eating at the outdoor cafeteria, looking out from a second-story railing toward the ocean. It's the kind of idyllic campus scene one might see on TV - which is only fitting, because you will. An actual high school situated in this tony beachside town, a short drive down Sunset from Beverly Hills, has been converted into the set of "Popular," the quintessential program of the 1999-2000 TV season. Here, 20-something actors pretend to be teens for a show that a bunch of 40-something TV executives hope will draw an audience of 12- to 34-year-olds. That's show business! There are eight new shows that fit that exact MO. Add in the ones that reverse the premise - shows about 20-somethings that teen-agers will want to watch - and you're easily talking a third, if not one-half, of the new kids on the TV block. Shows like "Roswell" (aliens mingle with teens), "Wasteland" (life after college in New York), "Safe Harbor" (single dad, teen-age sons), "Mission Hill" (cartoon slackers), "Get Real" (kids struggle with school by day, parents by night), "Freaks and Geeks" (same deal, but in 1980) and "Manchester Prep" (title says it all). And, yes, "Popular," which ironically may be the least pandering of the bunch but has taken the name that perfectly captures this acne-riddled trend. After all, who gets anywhere in life just by winning popularity contests? Answer: teen-agers and TV executives. Indeed, five of the six networks rushed at least one program onto its fall schedule containing such teen-angst staples as cliques, peer pressure, absurdist grown-ups and, of course, moist inter-gender relations. "The other networks have completely focused on the teens, the 18-to-34 and the 18-to-49 audience," says Nancy Tellem, entertainment president of CBS, the one network to buck the trend. "Their programming has become indistinguishable." And the people we have to thank for this adolescent surge are the executives at the WB. The network's total Nielsen numbers lag far behind the big four but, by Madison Avenue's standards, they're hotter than a Britney Spears chat room. The WB targets only 12- to 34-year-olds; its median viewer is age 26, making it by far the "youngest" of the six networks. WB viewers have record amounts of disposable income and spend it on movies, music and eating out. Advertising research also shows younger viewers more open to switching brands (though other networks, notably CBS, argue otherwise). After floundering its first two years with a sitcom-heavy lineup, the WB changed course to one-hour shows in 1997. It started with a tongue-in-cheek thriller, "Buffy the Vampire Slayer," that cast the daily traumas of high school life against a backdrop of a town infested by underworld demons. Fronted by its star, Sarah Michelle Gellar, and her fetching on-screen beau David Boreanaz, "Buffy" became the archetypal 12- to 34-year-old show. High school was a ruse, an excuse to load up the show's cast with fresh-scrubbed beauties, while the scripts played more to the ironic, unflappable tastes of slightly older viewers. Then in 1998, with the arrival of "Dawson's Creek," the WB took off. Besides creating two instant teen idols in Katie Holmes and James Van Der Beek, "Dawson's Creek" also made it fashionable to write soap operas for adolescents. Last season another WB soaper, "Felicity," followed in "Dawson's" footsteps, and this year "Jack and Jill" plans to do the same. Although WB shows aren't even in Nielsen's top 100 overall, "Dawson's Creek" was No. 9 among teens and the WB placed nine shows among last year's top 50 among the 12-to-17 age group. (The network's top-rated show is actually the wholesome but teen-friendly "7th Heaven," about a minister, his wife and their oversized family. The WB also had six of the top 10 programs among black teens, led by "The Steve Harvey Show. ") The WB is equally impressive among 18- to 34-year-old viewers who like fast food, the Gap, sporty but sensible cars and using their MasterCard. Last season the WB was the only network that didn't lose viewership in this age group - ratings, in fact, were up 11 percent. So now the other networks are playing catchup and trying to cash in on the surge in teen (and post-teen) spirit. "Every year there's a particular trend, and this year it's this big blowout of Generation Y," says Ryan Murphy, the co-creator of "Popular. " "Everybody wants on that bandwagon." As evidence, consider the feeding frenzy that took place late last year when Murphy and Gina Matthews were shopping "Popular" to the networks. ABC, NBC, Fox, the WB and even CBS made offers. Ultimately, Murphy says, the WB won out "because they're smart about creative decisions, they give you a lot of license, and they really know how to market these shows." Murphy says "Popular" is a deceptive show because, while seeming to chronicle the cruelties of teenagerdom, it's really about that grown-up and more universal urge, ambition. As such, it's less about Brooke, the sassy blond cheerleader played by Leslie Bibb, than it is about Sam (Carly Pope), the editor of the school paper, who's determined to ignore the stifling culture of cool as well as insecurities about her own self-image. (The two girls' paths merge unavoidably when Sam's mother and Brooke's father get engaged.) Surveying the WB's schedule, it is not hard to see the convergence of artistic expression and brand management. "Buffy the Vampire Slayer" has been matched on Tuesday nights with its spinoff, "Angel," starring Boreanaz. On Wednesdays, "Dawson's Creek" leads into "Roswell," an equally agreeable pairing despite the latter's "X-Files" ingredient. On Sundays two coming-of-age relationship dramas form a tandem, "Felicity" and "Jack and Jill." The WB's entertainment president Susanne Daniels says that's the way you build viewer loyalty: by having a schedule that's wall-to-wall with shows tailored to their niche tastes. Other networks are free to imitate the WB's program selections, she says, but they can't imitate its schedule. Case in point: On Thursdays ABC surrounds "Wasteland," a new 20-something drama from "Dawson's Creek" creator Kevin Williamson, with a game show and a newsmagazine, neither of which is likely to help "Wasteland" build an audience. - To reach Aaron Barnhart, television writer for The Star, phone (816) 234-4790 or visit the TV Barn Web site at www.tvbarn.com @ART CAPTION:The nine-member ensemble that will play high school this fall on the WB show "Popular," premiering at 8 tonight on Channel 62