Great news we just announced today the new Exchange Online mailbox quotas are now 50GB in size with no price increase. You get double mailbox storage for FREE and it will also be applied to any existing mailboxes you have in production with no extra steps required!
It is starting to rollout to tenants today and will continue through November. So you now get massive mailboxes in Office 365 education which should provide plenty of mail storage for faculty, staff and students for quite a long time.
Here is a matrix with all the new storage quota details:
Please read the official blog post here for more details.