I wasn't aware that it was a problem to disclose the discount offered - I had a (quick) flick through the terms and conditions of the standard educational store & couldn't find anything. If I'm wrong, let me know & I'll correct the post.
The college I'm with has negotiated special rates on everything except iPods - to get a discount on these, you have to go through the normal educational store. When I bought my new 5G before Christmas, I got a 10% discount.