For what it's worth, I went to Macrob. For Chemistry, I averaged 55-65% and got a high 30s SS (the exam wasn't too difficult that year). I'm not really what average SAC scores are like for corresponding subjects at MHS, although I have heard that 50-60% scores for Methods are fairly common there. I'm not in a position to provide predictions or anything like that as such but it's mainly depends on your rank in the cohort, for example, at Mac.rob the median scores for Chemistry and Methods are 36-37, so if you are below average in the cohort, it's unlikely you'll get 40+ unless you make significant improvement and ace the exam. There's also about 15 in the cohort every year who get 20-25 for Methods. Similarly in MHS, approximately 30% of students got below 90 ATARs, these students were most likely not ranked highly. I'm not trying to scare you off here, but I think that students in selective school assume that SAC scaling will solve everything and get complacent as a result. But yes, with hard work and some help from subject scaling (I know that in high-performing subjects like English at Mac.rob, it's possible to get scaled up by 3 letter grade brackets like B to A+), respectable scores are not out of reach.