It’s 1:15 on a Monday afternoon, and two dozen kids, mostly girls in brightly colored leggings, are in the gymnastics studio at Asphalt Green on 90th Street and York Avenue, doing what kids in gymnastics classes do. They’re stretching against a wall, palms pressed flat, arms overhead. They’re jumping and fidgeting on a puffy mat as an instructor demonstrates tumbling moves. Up in the balcony, meanwhile, their moms are in semi-distracted kid-tending mode. With one eye, they’re observing their blossoming Gabby Douglases, while with the other they’re reading their iPads, chatting with one another, keeping track of smaller children -- or all of the above.