Here’s the deal:
When you buy a new qualifying Mac with Apple education pricing* from June 16, 2011, through September 20, 2011, you’ll get a $100 Back to School Card to use on the Mac App Store, the App Store, the iTunes Store, and the iBookstore.
I’m not sure exactly when Apple started doing their Back to School offer for students, but for the better part of the last decade they have been essentially giving away free iPods with the purchase of a Mac to qualifying students in the summer.
This year marks a big change in the deal, whereby you’ll receive an iTunes/App Store gift card instead of a “free” iPod. Still, it’s an awesome incentive on top of already discounted prices for students.