so say you're ranked first in the class, with 86% on the sac (and say this is the average for the year) would that correlate to an A+ in your GA1/2 (non-science subject)
Half your study score is YOUR exam score.
The other half is: the exam score from your school that has the same ranking as your SAC ranking. If you're highest in SACs, you get given the highest exam score for your SAC mark. If you're second in SACs, you get the second-highest exam score for your SAC mark. If you're last in SACs, you get the lowest exam score for your SAC mark.
The marks your teacher gave you all on your SACs is entirely irrelevant.
To see how well you need to do on the exam to get a particular study score, check the VCE stats on the VCAA page. For example, in Legal you need about 90% for an A+, and if you get an A+ on both SACs and exam you start to break into the 40s. ***Not 90% from your teacher - 90% AFTER they do that score-matching exercise described above***
In other words, beat everyone else in your school in SACs, and then make sure ALL of you kill it in the exam (as in, share notes and help the weaker people prepare, too). Forget the exact percentage your teacher gives you. It doesn't mean anything.