10.13 b says:
"The official scorer shall charge a catcher with a passed ball when the catcher fails to
hold or to control a legally pitched ball that should have been held or controlled with
ordinary effort, thereby permitting a runner or runners to advance. When the third strike is a passed ball, permitting the batter to reach first base, the official scorer
shall score a strikeout and a passed ball."
So, it could be argued that the catcher didn't "control" the ball, in which case it is a passed ball, and not an earned run, nor an error on the catcher. In a game with 12 year olds, I'd be inclined to score it that way.