Your ATAR is calculated like this, moderated school marks + HSC exam marks = HSC mark thus your ATAR. But ... the its complicated, hahah. So basically through out year 12, you will do exams and hand in assessments. They are all in which make up your raw school assessment mark. You don't receive your overall assessment marks because at the end of year 12 they are sent to the BOS. Your school assessment will then be moderated according to how well or shit your school performed, but from your ranks you seem to be doing extremely well so I would worry so much. But moderation of marks means that your school assessment marks will change slightly depending on performance of the class. Your ranks however wont change.
In the HSC exam, you will do your exams and once they are marked, you will receive your mark. The BOS then use your HSC exam mark and add it to your moderated school mark and then find the average. For example, in advanced english you got 80% in your internals (so your moderated school mark) and you got 90 in your externals (HSC exam) the average will then be 85. So you will receive a HSC mark of 85 for advanced english. This mark is then scaled according to how well everyone performed from other schools and international students (kids from outside of Australia do HSC too)
From your scaled marks they will add them all up, it will be out of 500 and then your atar is calculated. Also depending on the difficulty of the course is reflected in the scaling of subjects. For example in Advanced maths if a kid got 50 and a kid in general got the same, the advanced maths kid will be scaled higher because the course is more difficult. I know we all think BOS is evil but they try to be unbiased as possible. I go to a selective school in the west and the markers at my school are stingy with marks so they take this into consideration too. Also there is a difference with lets a kid getting 60% in english and ranking 1st out of 30 in comparison to a kid getting 80% and ranked 1st out of 100 for example. All of this is taken in consideration when calculating the ATAR.
