I might be a little late for this, but going to post anyway
Going to SMSHS was one of the best decisions I've ever made
I personally got a >99 ATAR going there (with Math amd Sciemce subjects)
And a few others did too (a couple of them with Humanities subjects), and heaps got >90 in the grade
Of course some don't do as academically well there, but their skills lay in other areas
I think the thing that SMSHS does really well is encourage you pursue your goals and be the best you can at them, whether they lie within or outside of academia
I know people now who are succeeding in all walks of life
And of the >450 people in my grade, I can't think of anyone that didn't seem to enjoy it. We all had an excellent time there, and it keeps students happy and balanced, which helps them do better in their studies
If you're academically driven, St Marys gives you all the tools you need to do well, and its reflected by the rank it has relative to the area its in
That being said, expressions of interest for SMSHS 2016 closed a while ago.
I also know nothing about Oakhill, so I'm definitely not saying SMSHS is better or anything, because I don't know. But my experience (and the majority of my peers) was excellent with SMSHS, and I'd recommend it to anyone.
If your goal is academic achievement, SMSHS is not the best school. A lot of the teachers are pretty bad, the majority of the school leaves things to the last minute, the average across all the subjects is around 50% and its constantly a competition for who is the least prepared for an exam, meaning the competition for good ranks is very limited.
The schools best subjects are English, PDHPE, Business and legal, and the worst subjects are Economics and the Maths and Sciences.
Not true in my experience. Averages were higher than that and there was a typical bell curve distribution of marks, which is perfect for ranking.
Also the Maths at SMSHS is great, my Maths teacher was my best teacher in all of my schooling. And there are plenty of other subjects SMSHS is great for (Art, Music, Entertainment, Photography, Senior Science, Textiles and Design, History etc.)
Obviously this is all my (obviously positively biased) opinion based on my own experiences and those of my peers, so take it as you will.