UPDATE: According to Mashable, Apple has removed the requirement. No statements have been made. It's simply gone back to the way it used to be.
Since the beginning of Apple's production of computers, they have focused on education. It was a strategy to get their computers in front of people at a time when a computer seemed unnecessary. The educational market has always been important to Apple. Every year they run back-to-school promotions and they have always offered discounts for students and teachers.
However, now you will have to prove you qualify as Apple has done away with the honor system. Jon Porter at The Verge has more:
It’s not clear exactly when its policy changed, but at some point this month, some Reddit users noticed that Apple’s education pricing page was updated to note that customers will now be checked by Unidays, a third-party verification service.
As well as requiring Unidays, Apple is also placing new limits on how many items you can buy with an educational discount. Apple Track reports that users are limited to one desktop computer, one Mac mini, one laptop, two iPads, and two accessories per year.
The Verge
I would like to hope this change comes not from some bad apples ruining the program but from Apple looking to ensure people who get these discounts are the ones who actually qualify for them. I will choose to believe the latter until proven otherwise and keep some faith in humanity.