Also an issue of culture, if you come from a family where you're well off then it's likely that your parents are some sort of professionals who would have had a good academic background. This means that they're more likely to respect education more and understand that it is important.
Kids who come from less well off families where their parents might not have had great education, or have had bad experiences with education will view it in a different light, thus, not instilling that culture of respecting education in their children.
I think it's more of an issue than just private schools, tutoring and other luxuries. Culture also plays a big part - this is exactly why there are so many kids in private schools that end up doing badly in VCE whilst many other kids who go to average-ish schools who end up doing very very well.
It's a range of factors which add up, in reality. It's not due to any specific factors, but rather the interplay and connection between these factors and the glue which seals the gap which ends up helping some kids perform better than others in VCE.
Kinda agreeing with Paul and disagreeing at the same time. I agree that its a range of factors (lets face it, if you are that determined to do something in most cases there is little to stop you, within reason that is). What I would say, and this is just what I've observed (so anecdotal evidence), is that those who are more well off (on this side) are those who slack and don't utilise school as "they don't need to". Where as those who are less well off are the ones who are motivated to try hard and do well, as its the way to say "jump forward" if that makes any sense, but then there are the opposite cases too. BUT that doesn't mean everyone who is well off/not well off is like this. It really comes down to
you, what effort
you put in, how determined
you are. Although being "better off" would help in the sense that in more cases you wouldn't have to "go looking for the tools" to try and help you and to do better. Where as those of us who didn't have this have to spend time looking for and going after these tools (could say AN was a lifesaver in this regard).
So what I'm trying to say is,
on average it would appear that students from a higher socio economic background perform better, but just because you're not doesn't mean you can't too, it's just harder to, it takes more effort, it's not a level playing field from the get go.
Private School - Means you get to be around smarter students. This will dictate your interests and raise the bar for all your standards. Not to mention the better teachers and facilities would certainly help.
Also I wouldn't necessarily agree with this in all cases, just because someone is at a private school doesn't mean that the students are smarter (in some cases it just means the parents may value their education of their children more than others, but that still doesn't mean that the students will perform better, its up to the student, not the parents, if the student doesn't care then they won't perform as well. And just because the parents care doesn't necessarily mean the student cares/will care).