Document it like no other. Mention the pull out law that way it's documented that you at least warned them about it.

If admin asks you about the band's progress, size, etc then you can pull out those receipts. It's a long and painful waiting game.

I've also heard some schools where the director will have a meeting with the principal over it, but other campus principals will sit in to help mediate and help get that principal to understand the dilemma.