The raw school assessment marks are not taken into account by NESA, and they don't directly affect the student's ATAR. What will be taken into account however, is the ''rank order'' of the student as well as the relative gaps between the student and their peers. The school will also modify the marks before submitting it to NESA (even though nesa doesn't care about the actual marks), whilst maintaining the student's rank and the ratio of their relative gaps.
So basically, NESA doesn't care about the exact marks submitted by the school, all that matters is the rank and how far she is from her group and the students who are ranking at the top, which if you think about is kind of fair, since selective and high ranking schools tend to have harder assessment tasks. It wouldn't be fair for example, to compare a student's school assessment mark in maths ext 2 who attended Sydney boys with another who attended Birrong boys, the standards and difficulty of the exams are just too different.
On the day of the results, students will receive three marks for each of their subjects, their HSC examination mark, the assessment mark and the final HSC mark. For the HSC mark, it's determined by the student's individual performance in their HSC exam, ( it's not their exact (raw) mark, it's a scaled version of that). The second mark is based on the student's rank, the relative gaps between students, and the school's performance in that subject.( for a top selective school, the performance is almost guaranteed). The third is just an average between the two. More details on that is in the link at the end of post and here is a link to a youtube video by NESA about school assessment marks:
https://www.youtube.com/watch?time_continue=166&v=5qXs9id0Rjc
Now since she goes to a selective school that's ranked in the top 4 in the state, the number of band 6's (90+) achieved in each subject should be high, if we take James Ruse as an example, they had around 38 band 6s in English ext 1, so that means for someone who goes James ruse and is aiming for a 90+ in ext English, they should be aiming to rank in the top 38 in their class, of course this number changes yearly, but you can see some consistencies over the years and based on that you can conclude that for someone to achieve a 90+ in James ruse in eng ext 1, they should rank in the top 30.
This is just an example, so the numbers might be a bit off, but I guess this makes the idea a bit clearer.
So if the school that your daughter attends had for example an average of 30 bands 6s in economics, then she should be aiming to stay in the top 25 if she wishes to achieve a band6 and the same process goes for her other subjects. Judging her ranks based on the information you've provided is a bit tricky here, since the number of band 6s is different at different schools, but since it's a top selective school and let's say she's aiming for 97-98+ ATAR, I'd say she needs to improve her ranking and probably jump to the top 40% and this is just an educated guess.
And finally, you mentioned she's only done 40% of her assessments, this means she HAS 60% LEFT, and she can definitely turn the tables here. I personally had gone through something similar for one my subjects when I was in year 12, where I crashed in one very big assessment (I think it was worth 35%) and still managed to turn the tables, I ended up coming first in my trials and second overall, and you can hear many many stories like this from a lot of students where they made a comeback after crashing in some school assessment and ended up performing amazingly. Her task will obviously be harder since she attends a very competitive school but there is certainly more than enough time to make a difference,
and even If she wasn't completely happy at the end with her ranks or let's say she came close but didn't end up ranking in that group that is expected to get a band6, she shouldn't lose hope, she should try to smash the HSC exams, because If she performs very well in the actual HSC exam, she might still be able to break through that band6 or even higher and the worst case would be coming very close to getting a band6 which shouldn't really have a significant effect on her ATAR.
If you'd like to know more about how scaling/moderation/school assessments work and how NESA handles students' marks, Here is a fairly detailed explanation on how all of that works.
http://educationstandards.nsw.edu.au/wps/portal/nesa/11-12/hsc/about-HSC/moderation
To see a practical example of how marks are translated into an ATAR, check out some ATAR calculators, I found Matrix Atar calculator to be somewhat accurate, note that the marks you enter should be a prediction of what
the final HSC marks are going to be.
Although worrying ( or caring) about marks and ranking can be good and even act as a motivation for some students to keep going, worrying too much about the results can be detrimental to the students and even the parents well-being and it certainly won't help in improving their marks. I'd suggest to keep the ranks and the marks at the back of her head and just start working harder, try to figure out what went wrong and pick it up from there, and just to stay consistent with her studies overall, the results will most certainly follow. All the best!
