At 12u this play is effective, especially if there is a runner looking to advance, but really it's up to the catcher to understand the batter has nowhere to go. No reason for it to be a dead ball.
My other favorite at 12u was the casual stroll from first to second by the base runner, while there was a kid on third. This often times leads to the pitcher either balking or throwing over to first/second and getting into a pickle situation as the kid on third scores during the confusion.