so when u complete your hsc you get a RAW mark. this is the exact mark u get in the exam. then, depending on your school, it will get either pulled up or down. if u go to a very good school and do poorly in your hsc, your mark will be pulled up significantly, but the higher your raw mark, the less effect this will have. then this SCALED mark will be averaged with your adjusted internals mark (this is the trials, mid-years and everything in between) to get your final score to be judged for the ATAR. im pretty sure this is how it works