Typically no, holiday sales cannot be stacked with the educational discount.
When I picked up my 15" Retina MBP 2.3, 16, 512, 750M it was regularly $2649 in Canada, I got it for $2449 with education discount. I doubt on Black Friday they will go more then $200 off a MBP so buy with education discount now if you are going for the 15".