refer to Lear's post.
Anybody with common sense can see those socioeconomically better off have the opportunity to achieve higher outcomes than those with a lower SES. I italicise opportunity because it is how the student utilises the resources they have that makes the difference.
Consider things like tutors, textbook/subject-specific resources (as you have mentioned), significant teaching resources available to teachers (often seen in independent schools). As a teacher we can only work with what we have - and esp. in the government system it can be quite tough. Unfortunately there is a significant divide and only a small minority of those from a lower SES don't fall through the cracks and still achieve the same as if they'd have had access to such materials. It's not going away anytime soon.
Tutors = cost (in most cases)
Textbooks/resources = cost
Significant teaching resources = government schools rely on government funding to operate pretty much everything, to keep in line with the whole 'accessibility' mantra. Independent schools on the other hand benefit from both government funding along with parent investment through tuition fees, donations etc.
I've worked in schools where even student access to internet at home is a challenge - we take a lot of these things for granted but I'd like everybody who reads this to just realise and understand that there are those out there who don't have same luxuries and obviously this impacts an ability to be competitive when they reach VCE.
Put simply (if we use this scenario):
* Student A's parents can afford to pay a tutor for x or y subject
* Student B can't access a tutor because for their family, its a decision of whether they eat for the week, live under a roof (e.g. pay a mortgage/pay rent), have access to electricity/bare essentials.
I don't blame those financially better off - not in the slightest. But I'm outlining the realities faced (and if you don't believe this happens, I'd very strongly encourage you to go to a significantly disadvantaged school for a week and then come back to me and still say you don't believe it) by many students. There is a significant gap and again, it's not going away anytime soon.