I personally don't feel that the desire to do well is a separate issue. There are numerous cases where Student A at a public school performs at a higher standard than Student B at a high-tier private school simply because Student A is motivated and genuinely cares about their education.
These are just that; individual cases. Motivation and personal drive is a separate issue in that it is (mostly) a property of the individual student ie not something that we can really use to assess which school is 'better'. Nobody has said it's not possible to do well at a public school nor is it guaranteed at a private school. I speak to the average case, where I think being in a private school will be advantageous over a public school.
Russ: Would you mind elaborating on the reasons why you feel that it is easier to obtain higher scores at a private school?
Sure. I believe private schools more likely to have;
Higher quality of teacher
Higher quality of facilities
More established academic programs for advanced students
Increased availability of academic resources and support services
Better measurable markers (eg smaller class sizes)
Higher expectations of students
I believe these (in addition to other ones, this is just off the top of my head) all contribute positively to educational outcomes and do so to a greater extent than would be expected at a government school.
If you go to
this website and sort by median ATAR you get a rank of schools. The fact that MacRob is at the top of that list proves that you don't need to go to a private school to get a good ATAR score. The fact that of the next ~20 schools, 19 are private, indicates to me that it certainly does help. I think that given the large number of reasons to believe that private schools provide better quality education it is not unreasonable to believe that they do. It's perfectly plausible that I'm being misled by heuristics/logic in interpreting these statements (Linda is just a bank teller!) but I don't think that to be the case.
http://www.theage.com.au/victoria/high-school-fees-dont-equate-to-higher-wages-20140816-104swb.html
This is discussing employment outcomes post university (I read the same article a few days ago in the paper) and is irrelevant in a discussion of ATAR score. It's interesting for different reasons.
http://www.theaustralian.com.au/news/features/money-cant-guarantee-a-good-education/story-e6frg8h6-1226808835031?nk=9fad59bfcfdf2a78ef419e7a12ac9d1d
This one manages to avoid presenting much in the way of actual research I can evaluate. It catalogs a series of desirable qualities in a school but doesn't actually address the public/private debate directly. He makes the point that you aren't guaranteed good academic results at a private school (which I agree with) but that doesn't mean that private schools don't make it easier to obtain a higher ATAR. His description of a 'perfect' school makes no mention of private/public and in fact concedes at the end of his article that it's hard to find schools like these in the public system.