What I really wanted to ask was, can I still achieve a high study score + ATAR if I’m not ranked one in all of my subjects? Someone told me, (not sure how accurate this is) that you can’t achieve a higher study score than the person ranked one on your class even if you do perform higher than them in the exam.
Nah, you can get a higher SS for sure even if you believe it's a bad cohort. Assuming your cohort is >30 people or so, you'll be perfectly fine - it's easy to overtake others in SS as long as you aim to improve on SACs, and ultimately, be the best in your exams.
1 data point: me in Physics - good school but very easy SACs for this subject so everyone did well - drop some silly marks and my rank dropped to the 50th percentile. Final study score: tied highest in my cohort (historically not as good as previous years' cohorts but it is what it is).
Even if you have a bad cohort and don't get an amazing SS out of 50, relative to others you have every opportunity to get a higher SS than the current rank 1. Exam rules.