Depending on the country or region you are located in, the details will vary; to
contact an education store see the link in the bottom of the Apple Store page.
Not knowing where you are located, here are some leads to check into...
To find an Apple education store, in the global sense, see:
http://store.apple.com/us-hed/browse/open/country_selector
For the Apple (US) education store, see:
http://store.apple.com/us-hed/help/contact
For additional links to Apple US education content:
For other access, you may try a regional or country source and then ask if
they can help you; should you be unable to find an appropriate ED link.
For authorized Sales, Service, consulting, training, certification, (global)
https://locate.apple.com/country
Ideally, if you know ahead of time the highest requirement of a system
or product you may need, to buy it ahead is always the best bet; now
since computers come with a pre-installed non-user accessible RAM
or other components, this is more important. Also, combine your order
so once a year, you get what you need.
There are limits and in some instances so there is no doubt about who
is getting the discount; since excess could be diverted to other persons
who may not qualify. However if you have siblings in your household,
and live at home, they may qualify separately to get student discount.
Good luck & happy computing! 🙂