As ajc196 accurately notes above, 5600 A3 licenses will allocate: 5600 x 50GB + 100TB per school = 380TB, as Microsoft clearly confirms:
« The total pooled storage limit is the maximum amount of storage that can be used across your combined users. For A3 or A5 licenses, use this calculation: 100TB + (number of A3 paid users x 50GB) + (number of A5 paid users × 100 GB) + (additional storage purchased) = capacity/limit. »
Ref: https://www.microsoft.com/en-ca/education/products/microsoft-365-storage-options#StorageLimitsItemId
Another way of summarizing Microsoft's new allocation policy is:
A3 and A5 license holders will have their storage allocation for OneDrive reduced to ZERO.
Furthermore, the 40 Student Use Benefit licenses that accompany each A3 and A5 license, will now have ZERO storage allocation—for both OneDrive and Email.
Yes, 100TB will be allocated per school, but this, perplexingly, is independent of the number of A3 & A5 licenses or the number students! Any large higherEd institution will therefore be in the position of trying to dole out this 100TB allocation to provide, not only sufficient OneDrive storage for their faculty and staff, but also to provide any OneDrive or email storage for their 10's of thousands of students.
The only conclusion that I can draw is that Microsoft is signalling to its M365 higherEd customers to STOP using OneDrive, and to STOP providing students with email. And to rethink their business cases to migrate research or institutional data to M365.