I think the problem with that would be it accentuate the problem of economic differences amongst students. This is mostly in reference to students who have the privilege of going to tutoring centres and etc. It would also stop students from essentially growing throughout the year, by applying the mentioned system, students would simply tested instead of learning. The problems that will arise will be similar to the problems found in Singaporean and Chinese education systems where the education system becomes less educational but more competitional -> Due to Australia's tall poppy syndrome, it can deducted that such system won't work in the broader Australian public.
I get what you're trying to say but unfortunately this is the state of the education system anyways. Even in school, whether it be the internal or external assessment, at the end of the day students care about marks more than learning because of the incentive it provides to the ATAR. The ATAR has essentially reduced education into a numbers game the focus is no longer on intellectual curiosity or genuine understanding, but on how effectively you can maximise marks.
This is why tutoring centres thrive: they’re not really about teaching deeper knowledge, but about “teaching to the test” and drilling exam strategies. So even if we kept the current system, the inequality you mentioned already exists those with resources will always have an advantage. At least if the system was standardised or externally marked across the board, students might feel like they’re being measured on the same scale, instead of dealing with inconsistent internal assessments that vary in difficulty and generosity depending on the school.
In the end, the problem isn’t whether one system is
perfectly fair, but which system best reduces existing biases. Right now, schools with more funding, better teachers, and more external support already give their students an advantage. So while any change won’t magically solve the issue of privilege, it could at least shift the focus away from how much a school inflates marks, and more onto consistent standards across the state.