As increasing numbers of parents keep their children from playing tackle football for safety reasons, the National Football League and other groups have sought to reassure them that the game is becoming less dangerous.

No initiative has received more backing and attention than Heads Up Football, a series of in-person and online courses for coaches to learn better safety procedures and proper tackling drills. The N.F.L. funds and heavily promotes the program. The league and U.S.A. Football, youth football’s governing body, which oversees the program, have sold Heads Up Football to thousands of leagues and parents as having been proved effective — telling them that an independent study showed the program reducing injuries by 76 percent and concussions by about 30 percent.

That study, published in July 2015, showed no such thing, a review by The New York Times has found. The research and interviews with people involved with it indicate, rather, that Heads Up Football showed no demonstrable effect on concussions during the study, and significantly less effect on injuries over all, than U.S.A. Football and the league have claimed in settings ranging from online materials to congressional testimony.

As the 2016 youth football season dawns, the revelation will most likely fuel skeptics of football’s claims of reform, and discourage parents who want solid information about the sport’s risks for their children.