According to the school, the coach was praying at the 50-yard line at the conclusion of the game, before players had been released to go by the coach, and while the coach was still on paid time (in the pictures the players are still wearing their uniforms and have their pads on, indicating that the prayer was immediately after the game).
Having played numerous school sports, I can't recall a time when as soon as the game was over, we players were allowed to just leave. Typically there was at least a team huddle with the coach (most often an actual summary, sit-down session), followed by additional post-game activities (showers, medical treatment, equipment collection, clean up).