I got confirmation last night from SheerID of what we all expected was the case:
Thank you for contacting SheerID regarding your interest in Apple Creator Studio. I’m sorry to hear you experienced an issue confirming your eligibility. Allow me to clarify the guidelines for this offer.
At this time, Apple has made the offer available only to students and faculty members enrolled and employed at degree-granting colleges and universities. Since your school is classified as a high school, you do not meet the eligibility requirements.
As a third-party verification company, we partner with many retailers that have unique sets of guidelines for their exclusive offers. These guidelines are provided to SheerID to follow when verifying eligibility as securely and accurately as possible. We are unable to provide exceptions or make alterations to them. I hope you understand my support limitations in this case.
For more information, you may contact Apple Support here.
We appreciate your understanding.
Kind Regards,
Myka G.
Sr. Verification Support
SheerID
We're also an iPad 1-to-1 district and I'm sitting at my desk in my classroom right now typing this on my district-provided MacBook (with my district iPad right next to it). I use Keynote and Pages every single day. This seems like a very short-sighted decision, Apple. Too bad.