It's weird how I never had to "prove" I was a teacher when ordering online from Apple.
Some years ago (maybe like 7 or 8), I purchased something with the discount at a physical Apple Store, and I needed to show ID to prove I was actually a teacher.
But I ordered multiple times online and never had any questions asked that I remember. (Maybe they have it registered from the time I had to show ID at an Apple Store, but even then, I could have switched job since then ...) (Tim Cook, if you're reading this, I'm still a teacher, just call me.)