"What's the first thing we do when we get to our bike?" David Gesualdi asks his second-graders. "Check the air!" they yell back at him.
His 19 students are sitting in a semicircle in the gym at Walker-Jones Education Campus, not far from the U.S. Capitol.
Decked out in blue helmets, hair nets (for lice protection) and bright orange mesh vests, their eyes shift impatiently between their phys-ed teacher and the racks of shiny new BMX bikes behind him.
First, though, he walks them through the A-B-C's: "Air. Brake. Chain."