An ATAR estimate would be useful because pinpointing your current level of performance can help determine the extent to which you can improve your overall performance through favourable HSC exam performance, that is, your ability and likelihood of reaching or exceeding an ATAR of 90. However, inferences can be made from the information that you provided. First, your school rank indicates that a reasonable number of band 6's/E4's would be achieved in your subjects each year. This would allow us to better understand your ranks and make reasonable assumptions regarding your current level of performance in each. For example, your rank in English Extension 2 is optimal. If you also achieve the highest mark in the external component for this subject, you will technically be able to maximise your overall HSC mark, allowing this subject to make a good contribution to your ATAR.
Similarly, your ranks in English Advanced and Mathematics Standard 2 seem good, meaning that you can likely expect a good Assessment Mark for each subject. Coupled with favourable HSC exam performance, you can achieve a good overall HSC mark in each subject, increasing the contribution made by each to your ATAR. By comparison, English Advanced and Mathematics Standard 2 can make a greater contribution to your ATAR than English Extension 2 because they are worth 2 units each, compared to 1 unit in the case of English Extension 2.
On the other hand, your position in the rest of your subjects is of a lower standard and at this stage may prevent you from achieving your ATAR goal. This is where you should focus most of your preparations because the better your HSC exam performance across those subjects, the better your overall performance will be in each, and the greater the contribution of each to your ATAR. Of course, since you are taking 12 units, 2 units worth of subjects (which can be one 2 unit subject, or two 1 unit subjects) will not count towards your ATAR.
Overall, I think that an ATAR of 90 is within reach, as long as you are able to perform favourably in the HSC exams of your lower-performing subjects.
I hope this helps!
