By using Apple's Volume Purchase Program (VPP) you can get a 50% discount for purchases of 20 or more apps.
Below we summarized the most important information about the process of how to become eligible for the special pricing.
You have two options to distribute the app to your students.
1. Redeemable Codes
The easiest way is to purchase app codes and share them with your students directly. One code is valid for one Apple ID. After a code has been redeemed, it is transfered permanently to the student.
2. Using Managed Distribution
By using this option, you can distribute purchased apps to your institution's devices. You also have the option to revoke and reassign apps to different users, so your institution retains full ownership and control of purchased apps.
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The first step is to enroll your school on school.apple.com. Once you are approved, your school will be eligible to get a 50% discount on all app purchases of 20 or more apps. Please contact Apple directly for more information about the enrollment.