yeah unfortunately busways doesn't offer concessions to students unless you get a specific pass from them. So as the others have said you go to the student centre and fill in a little pink form which has some details about yourself...name address etc, together with the hours you attend uni...then you get it stamped by someone in the student centre. You then take the form to your nearest busways depot and they will make it into a pass on the spot. I think you can mail it, but it may be quicker to take it, as they will do it over the counter while you wait. The only thing though is that with busways you'll have to supply a small photo, such as a passport photo...that will be glued to your concession pass as a form of identification...so make sure you have one handy when you're ready to get your pass
Though just to reiterate this pass does not entitle you to free travel, merely a discount on the full fare or adult price.
See the cityrail website for details about weekly passes on public buses etc
You can also get a "travel 10" pass on sydney buses which can be used for 10 trips, I think it's cheaper than paying separately and can be used whenever.
http://www.cityrail.com.au/fares/travelpass.jsp