Ruby Writer, Anna Grace Skrentny, Leah Kwiatkowski, and Izzy Santiago at Jellyfish Photo: Jeff MariniThe first thing 14-year-old Izzy Santiago and her friends do upon entering a restaurant is scout for the perfect place to take some photos for the image-sharing app Snapchat. Overthe course of the past few months, they have descended on the sun-dappled dining room ofSummer House Santa Monica, the glam steakhouse Maple & Ash, and the açai-bowl and green smoothie mecca LeftCoast. “Pretty much every time I go to a restaurant, I’mtaking a picture,” says Santiago, a freshman at Lane Tech.Phoebe Fisher, a Whitney Young freshman, started avidly sharing restaurant photos on Snapchat after she went to a birthday partyat the clubby Gold Coast sushi spot Jellyfish and noticed that nearly half the restaurant’s 105 seats werefilled with girls her age. “People were, like, lining up to take photos in front of this one blue wall, and then all through dinner, everyoneis just posting photos.”Fisher shares her Snapchatphotos with students from schools across the city andbeyond, all of whom are eager to post their own dining exploits. “A lot of it ishow you look and how you want to show yourself off, like, ‘Oh, look, I’m at Summer House in a nice dress and eating healthy and drinking this cool drink,’ ” she says.There are plenty of social media users who’ve built a following around food—though usually they’re old enough to order alcohol. But now a growing coterie of well-heeled Snapchatting teen girls (and it’s always girls) are staking their claim as influencers. In the time it takes for the photos to vanish from recipients’ feeds—24 hours—enough buzz has been created to spur a new onrush of youngdiners eager to spend their parents’ money at the hot spot du jour.Restaurateurs have begun to see a sizable—and bankable—uptick in high-school-age diners whospend like grownups. “It’s crazy,” says Michael Madden, founder of Left Coast, which has locations in River North and Lincoln Park. “They come from even as far as the northern suburbs on weekends with their parents, eight at a time.”The hype is often not even about the food. “If there’s good energy, cool lighting, cool seating, we’re more prone to want to go and take pictures,” says Anna Grace Skrentny, also a freshman at Lane Tech. “That’s how restaurants getahead with us.” Fisher agrees, citing Wicker Park’sMahalo—known more for its neon signage and swing-set seating than its culinary prowess—as an aesthetic ideal.Status plays a role, too, and spots popular with adult bigspenders, like Maple & Ash,have cachet with the teen set. “People like to flaunt that they’re going to these places,” says Skrentny. “Getting ready and dressed up is part of the fun.”Jeff Mahin, chef-partner at Summer House and severalother Lettuce Entertain You spots, doesn’t mind his tables being colonized by high school girls. “You can have an enormous advertising reach without paying for it,” he says. “They’re putting more energy into an Instagram post or a Snapchat story than they do their homework.”