Disney's Model Behavior demands a lot of most viewers. First there's the premise--that a typical tortured teenager could pull off trading places with a hot teen supermodel for a week based solely on a passing resemblance. And then there are the characters. Who's going to buy Party of Five's exceptionally pretty Maggie Lawson as class geek Alex Burrows, whose best friend lovingly describes her as a fellow dweebette? Or N Sync's Justin Timberlake as Jason Sharp, a real sweetheart of a guy who's trying to scrape together dough for grad school as the fashion industry's globetrotting pretty boy of the moment? Tweens, of course. While everybody else is putting his wallet away, kids from 8 to 13--Timberlake's gazillion girl groupies, especially--will be transfixed. This is completely wholesome stuff--Alex's parents are picture-perfect, family-values-promoting suburbanites, and even Kathie Lee Gifford, overbearing stage mom to supermodel Janine Adams (Lawson, with looser, swingier hair and no glasses), shows a softer, more considerate side by film's end. So do the scheming life swappers (surprise, surprise), who, after setting in motion a tsunami of confusion and heartbreak, work the grass-is-greener way of thinking out of their systems. The message--be yourself--is one that just might take with the sort of sweet, impressionable youths who can suspend disbelief long enough to lose themselves in this movie.