Foul tip hits home plate

[Spectator]

I was a spectator at a 5th-6th grade level baseball game and clearly saw a batter hit a foul tip. The ball shot straight down from the bat and hit the top edge of home plate to the right of the catcher’s right leg and then bounced approx. 12” further to the right of home plate. The catcher grabbed the ball thinking it was a foul; however the umpire called it a live ball. The player on third base made it home and the batter advanced to first base. I was always under the impression that if a foul tip directly hits home plate it is ruled a dead ball. Please explain.