I'm guessing the superintendent does not understand agriculture.

This might be an opportunity to invite the superintendent out to your farm sometime next year - at a time convenient to both of you.  Give him/ her a tour of your facilities. Explain the process of growing the crop, and the need to wait for it to dry down before harvest. Explain that you are bending over backwards to accommodate the school districts needs for this event.  Explain the need for the school district to communicate their needs up front.  Explain what it is costing you to accommodate their needs.  See if this approach has an impact.