I'm not HE, but I talked the sales guy into giving me Applecare @ the college rate. In the documentation I received, I didn't get a registration number to enrol in applecare (as you normally do). Turns out that you are normally automatically enrolled in Applecare when you purchase a support contract (such as the HE uplift), but that is linked to the serial number of your computer.
I was correctly enrolled, but it was attached to the wrong serial number (apparently I was supposed to receive a different computer, and someone else has my, APP-eligible unit). So if you've bought APP via Higher Education, it might be worthwhile calling tech support and asking them to verify that you were enrolled correctly.
When you talk to them, re-iterate that you've purchased it (and that it appears on your invoice & delivery slip), and ask for them to confirm your policy / contract number. After about an hour on the phone to tech support, they figured out the problem, and said that my APP was being transitted to the serial number of the computer I actually have, but I'm not fully convinced. Seems like fairly messy back-office process. But if you have the policy number, you should be fine.
For those buying from the HE website, it could be that all the computers are auto-enrolled in it - I think I only got documentation because I bought it seperately. But it wouldn't hurt checking that you have, indeed, been enrolled correctly.