I am not super experienced in these situations but what would it help if you brought it up and what would it hurt?
It might help the board/staff to hear the observation if it is from a "neutral" party. ( A mom whose kid is not in the Saturday school.
On the other hand, maybe you don't want to "rock the boat" if there is no direct benefit to you or your child and the school folks might then see you as someone who is butting in on an issue that is not your concern...
Maybe a compromise would be to say something, but just say it in a different forum. You have already spoken to the principal. Maybe you can talk to one of Sat. school parents privately and encourage them to step forward. Let them know you support them...
just some thoughts...
Good luck, EW