Attending a lower-ranked school does not necessarily mean that you will not be able to achieve favourable HSC results or ATAR. Outstanding performance is possible at any school, as long as you demonstrate commitment to your studies throughout year 11 and (more importantly) year 12. Essentially, performing at a high standard at a lower-ranked school that is equivalent to that of a student who attends a higher-ranked school will require you to place as high as possible across your subjects in year 12, which can be done by performing favourably in your school assessment tasks/exams. Subsequently, you will need to thoroughly prepare for your HSC exams in order to perform well in them too. Unlike internal performance, HSC exam performance is not affected by factors such as your school cohort.
In your particular case, you may wish to consider aspects of your school such as facilities, teaching quality and distractions (if applicable). If your school offers good facilities that may be helpful in terms of your studies, as well as good teachers, and if you experience little to no distraction from your peers, then there would be nothing stopping you from performing at a high standard.
Regarding your school rank,
Better Education is a website that lists school ranks based on HSC results. However, Whitebridge High School's rank is not published on this website, and there is a "PNO" comment, meaning that permission to publish this school's rank was not obtained. Despite this, we can still determine an approximate rank by considering the school's success rate, which involves determining an approximate total number of HSC exams sat by every HSC student, as well as the total number of band 6's/E4's achieved (this one we know), as follows:
This website states that this school had 77 HSC students in 2023. If we assume that each student took 5 subjects, this would result in 385 exams sat. Therefore:
Based on this, it would be reasonable to suggest that Whitebridge High School is ranked in the 300s.
I hope this helps!