Um not sure if people replying have actually done this or not, but I have purchased in store with educational discount twice.
The last time I did it was in July 2011 - OK, it wasn't very recent, but wasn't ages ago either and I doubt things changed. All you need to take is your student ID, they then have a list of Universities, you tell them which University and then they will take your ID number and confirm it.
Pretty simple procedure, and remember the discount differs on each product ALSO if you're planning upgrades remember you get discount on those too!
ALWAYS - Check the receipt, they have totally messed up the receipt twice for me!