You can get student discount at Apple Store but from memory the discount was between 4%-8%.
You're better off waiting for a JB Hifi or Dick Smith 10% off Apple computers sale (seems to happen every other week- keep an eye on OzBargain) and then getting it price matched at Apple Store if you really want to buy from there (since they accept AMEX).
Assuming they launch new Macbook Airs next week (which there are rumours they are) then you can expect discounts on old stock as retailers try to clear them if not closer to the day, or right after.