Educational discount policy at Apple and international student
If you select the Online Apple Store for your Country, and then at the bottom of the page click on the "Education Store" link - you'll see which options you have.

Some Institutions/Schools/Educations will give you a discount without any documentation - other requires a special log-in to the Apple Store (where you typically get a better discount).

All the above for the online Apple Store - if you can get a discount in a "real" Apple Store in a Country where you don't live, I don't know for sure - but I do know that it is possible in some places of the world, if you just show some School ID.