The science is clear: football players face high concussion risks, and repeated concussions can lead to brain damage. As youth participation in the sport declines, schools and professional leagues seek answers to the concussion crisis. Nicholas Schmidle travelled to St. Thomas Aquinas High School, in Fort Lauderdale, to report on the strategies its football program has put into place to cut the risks of head injuries. Schmidle spoke with Kivon Bennett, a young football player, whose father is the former N.F.L. pro Cornelius Bennett. After retiring from the Indianapolis Colts, Bennett was active on the Board of Former Players and fought the N.F.L. to recognize the risk of brain damage. But now that his son is playing, even Bennett chafes at some of the new rules that aim to protect players but change the way the game is played.