PHILADELPHIA (AP) — They'd all skipped caffeine at school and cut back on sugar to keep their heart rates down and their nerves steady. They donned thick canvas uniforms to hold their bodies rigid when they aimed. Some knelt. Some stood. A few lay prone on mats spread out on the cold floor. Just around 3:30 p.m., starting time for the Everett Area High School Rifle Team's practice, the teens loaded .22-caliber bullets into their rifles, $2,000 to $5,000 worth of hardware each, rested their cheeks on the stocks, and held their breath.

In the moment between each heartbeat, they fired. For the ne...