speedofsound, I went through every single ATAR in the 2009 ATAR thread, and out of the 20 99 ATAR's or more, ONE did Society and Culture. 17 did Maths Extension 1, 14 did Chemistry and/or Physics, 15 did Maths Extension 2, 5 did Extension 1 and/or 2 English. So really, at the uppermost ATARs - that is simple proof, vivid, true and real - that the highest ATARs are achieved most of the time by those who do the high scaling subjects.
By contrast, of the 104 people who posted their subject's and ATAR's this year - of the 20 who got less than 90 ATAR, only 1 did Maths Extension 1, 5 did Chemistry, 4 did Physics, none did Maths Extension 2 or the English equivalent, 3 did English Extension 1.
Furthermore, 9 of the 20 who got less than 90 did General Maths (in contrast to 7 who got 90+ but none got 99 or higher). 3 did Standard English, compared to 8 who got 90+ but none got over 99. Out of the 7 who did Society and Culture, 1 got 99 or higher, and 5 got from 90-99, while the outlier from it - one person - got an ATAR of less than 65.
Out of the 3 who reported Drama, 2 got less than 90 (although reported ATAR's of 80-90) while the other got 95 but did not break 99.
Sure this is very preliminary, but since I have tons of time on my hands - I could do this for last year's cohort, and the year before that, etc, etc, etc. Of course converting to ATAR from the UAI.
My conclusion is, it is very clear that those who get high ATAR's do high scaling subjects in general. The data for lower ATAR's does not have a large enough sample space to make observations.