Ilana Panich-Linsman for The New York Times
COLLEGE STATION, Tex. — On a steamy afternoon in June, Jim Poynter, the coach of the 7-on-7 touch football team at Lamar High School in Arlington, Tex., escorted one of his former players around the state tournament.
In a game last spring, the player, Brett Green Jr., was knocked out after his head collided with a teammate’s shoulder as they jumped to intercept a pass. Green was airlifted to a hospital, where bleeding in his brain was discovered. He spent weeks in the hospital recovering from dizziness, headaches and blurred vision, and had eye surgery and physical therapy.