This information is incorrect. Schools may allow only one purchase because they do leasing, offer a subsidy, etc. However, the official apple info is as follows:
"Who is Eligible To Purchase:
The following education individuals are eligible to purchase through the Apple Store for Education individuals:
Faculty or staff member of a public or private Higher Education Institution in the United States
Student currently attending or accepted into a public or private Higher Education Institution in the United States
Parent purchasing on behalf of their child who is a student currently attending or accepted into public or private Higher Education Institution in the United States
Purchase Quantity
Faculty, Staff and Students purchasing from the Apple Store for Education Individuals will be allowed to purchase the following quantities of product per academic school year:
Desktop: One (1) may be purchased per academic year
Mac mini: One (1) may be purchased per academic year
Notebook: One (1) may be purchased per academic year
Display: A maximum of two (2) may be purchased per academic year
Software: A maximum of two (2) per software title may be purchased per academic year
Apple TV: There is no limit on the quantity of Apple TV purchases per academic year
iPod: There is no limit on the quantity of iPod purchases per academic year"
I can't find the printed version, but I just bought a MacBook for my son, and it says "students, AND student's parents" qualify (obviously buying for a student) for a ONE TIME shot at such a discount, so there's no date expiration other than the 16th for the Nano offer. We just entered the uni where my son's enrolled, and went from there, but bought it on my account.