Where in your/our job description does it say "Donate $5,000-15,000 worth of your creative ability to the school unpaid?"
That's about what you pay an arranger and drillwriter, isn't it?
Why wouldn't you expect to get compensated for something you're perfectly willing to compensate someone else for?
Yes, there are legal issues - you'd have to submit bids or hire yourself as an independent contractor - but if you're willing to pay someone else to do it, you should be also willing to pay yourself for it.
Barring that, you should negotiate for that fee to be included in your stipend if you're going to be expected to do it. No football coach coordinates 100% of his team's actions. They hire someone to manage film, they have position and assistant coaches, and each of them is paid for their expertise and time.