um i think its a bit unfair.. because it also depends on the kind of school u go to
example.. i go to a crap public school and got 3 band 5's n 2 band 4's and got 71.1
my work friends brother goes to a good private school and got 1 band 5 and 4 band 4's.. he got 73
and we did 4/5 subjects the same
another example
a girl at my school got 82 and got 2 band 6's, 2 band 5's
my boyfriend goes to a private school and got 1 band 6, 2 band 5's and 2 band 4's and got 83
and they both did similar subjects
It's got nothing to do with the public-private dichotomy, if that's what you're insinuating. Your marks do get scaled up if the rest of your cohort performs well, which may have some correlation to the higher performance of private schools.
I don't think you can use those comparisons accurately to prove your point. Let's take the example of 'the girl at your school vs. your boyfriend'. The slight differences in their subjects, albeit being similar,
would have a bearing on that 1% ATAR difference. What if your boyfriend did ext 2 maths and she did ext 1? Moreover, you keep mentioning so and so got this many band 5s/6s, as did so and so, therefore shouldn't they have the same ATAR. Let's use the boyfriend example again, but before that let's establish what, say, a 'band 5' means. A band 5 is 80-89%. Now, what if your boyfriend was getting 88% band fives, and the girl at your school was getting 82% band fives. Naturally your boyfriend would receive the higher ATAR.
If your entire case is based on these two examples, then it is very tenuous indeed. You cannot compare things as general as "similar subjects", or "band 5s", in order to demonstrate that a 1%(girl vs boyfriend), or 1.9%(you vs work friends brother) ATAR difference has anything to do with what school you go to, let alone it being a public or private institution.
At the end of the day, the better you do as an individual, the less you need worry about scaling or how the rest of your cohort does.