If you have a Student ID on you, even if it's from five years ago (or more), and show it to them, 99% of the time they will most likely honor a student discount.
They don't check on the website it just says are you a student click here to pay less! I'll take the student discount to my grave and stack it with the 5% cashback through the Discover online store.
Be careful if you are ordering online and lie about your student status, they will check your name with the records of the university, and if it is determined that you are not a student, Apple will release a Lion to your house to come and EAT YOU ALIVE!
I have, but I'm a teacher so I still apply for the discount 😛
Seriously... Do what you will. It's like Apple's honor policy on prior OS releases: they're not going to check, but are counting on the honor system most of the time. Be responcible adults, mmm Kay?