I'm not sure why you're concerned about the average ATAR mark of your school, even if you were at a larger school it doesn't really have anything to do with the score you get or the scores that future Year 12 students at your school might get. There might be some kind of trend with the two, but that doesn't particularly mean anything. If you're the only person getting an ATAR from your school (unless others are doing the VCAL/VCE mix?), then you'd expect the average to be your ATAR.
For any statistical moderation they do on your sacs, well I'm assuming you're in a small group partnership with another school and all that has been dealt with. If you're not in a small group partnership, they have ways of dealing with that too.
I realise that it has no effect on my actual ATAR or scores or anything in general. It's just a number. Me and my friends from the neighbouring school in town were curious though as to what would happen, as I never get any straight answers from my teachers.
No other students in my year do VCE (two dropped out due to poor work ethic, the other five students do VCAL). But they've merged VCE with the other school, so I share classes with the catholic school kids. SAC marks are compared between the two schools, and sometimes a third school for smaller classes (I do chemistry with 2 other students, physics with 4 others).
Fun times.