The kid from left field (1953)

Coop's an ex-ballplayer is now a peanut vendor, who takes too much of an interest in the game. But he's passed on his craze for baseball to his son, Christie. When his dad gets fired, Chris makes friends with the former team owner's niece (and her boyfriend Pete), and not only gets his dad's job back, but a batboy position for himself. With his dad's help, Christie begins to make a few suggestions here and there. And as a publicity stunt, the team makes him their youngest manager on record. But when Chris gets sick, Coop has to come to the rescue.