Your school is -meant- to follow the guidelines for the dates provided by the CSSA.
If they choose to alter the date, they are still allowed, but chances are that a student will be smart enough to get a good reply from another friend who has already sat it about what is in the paper.
Also, god help you if the teacher follows the marking guideline for the CSSA paper for Physics/Chemistry.
In 2003, the answers were either wrong or the sample answer is not worth that band 6 they say it will get. If I recall correctly, at least 5 multiple choice questions in the Physics were wrong. And they provided 3 line answers to a 6 mark question....pathetic...
Anyways...good luck with your trials. The CSSA questions are indeed a very good practice test for the HSC. They provide really good questions that follow the format of the HSC.
Also, It would be greatly appreciated that when you receive your papers back to scan them and submit them to me or boredofstudies for other people to try.