As someone who went through the selective school system with MHS a few years ago, I think the most important thing about the school you choose should be the culture. Having just finished my degree in medicine, when I look back on my time at school, funnily enough I actually don't think about the good or bad teaching, the amount of practice exams I did, or how I wish I studied more or less - I think about my fellow students and the good times we had. And when you eventually come to 5 year reunions and the like as an Old Boy, those are the anecdotes we're sharing and having a laugh about, not ones about academia. Please keep that in mind.
But of course, academia is important. And I'd be lying if I didn't say it was my #1 priority when I was at high school. Is the teaching the best at MHS? Probably not, it certainly wasn't amazing when I was there. I had some lackluster teachers, but also many brilliant and inspiring ones. As with any public school, it's a mixed bag. But I don't think the teaching needed to be amazing, because the cohort was amazing. The cohort drove each to success, it was an incredibly collaborative environment that didn't leave people behind, and indeed many went through to get 99+ ATARs with no or minimal tutoring (unlike the top NSW selective schools!). If you have a good teacher, that's great, but if not you still have each other and a culture and history of success and excellence that you don't get in many other schools in the country.
I'll share one example of what many of you youngsters would consider to be 'bad teaching' and how that's a rather narrow viewpoint. One of the teachers who made the biggest impact on me was someone who I probably learnt nothing academic from, he barely taught anything in class and spent most of the time sharing various life experiences and telling jokes. This, especially in retrospect, was incredibly valuable, it's not often you are forced to sit in front of someone as they impart life advice and create a fun atmosphere. Why was this so valuable? This teacher understood who he was teaching. He was teaching a driven cohort who he knew would study for hours at home regardless of what he said, indeed for many of us school was some of the most 'fun' we got on a regular weekday. So during class, and within reason, we could put our hair down in class. He'd help anyone that needed help, explain anything that needed to be explained, but didn't lecture us on maths like a traditionally 'good teacher' would. Don't let 'bad teaching' guide you away from MHS, it's often a blessing in disguise.
A final comment on this business of median ATARs and tutoring. Median ATARs are great to look at if you plan on being a median student. If you don't plan on being a median student, then the proverbial sky is the limit. Looking at median ATARs, in my opinion, is not useful for that reason. Tutoring, as has been alluded to earlier, is commonplace. Undoubtedly, it's common in any selective school and any top-tier school in Victoria. Personally, I did got some tutoring only for year 12 English (which I don't think helped much!), and did fine. I'm far from a genius. Many people did better than me with less tutoring. Tutoring is there if you need it, but you don't need it to do well. Keep that distinction in mind. Don't get sucked in to paying for some freshly graduated 99+ ATAR uni student who thinks they're all that to teach you what the textbooks already spell out, what you should get sucked into is maintaining your own personal drive to work hard, persist, and improve. That's what matters at the end of the day.
That stuff aside, I implore you to look outside of the academia of school before making your choice. MHS' unofficial motto is "more than just marks", and it truly lives up to that. It's from getting involved in extra-curricular activities that you'll form your fondest memories that you'll treasure for decades. You won't find another public school in the state with the resources that MHS has for sports, clubs of any sort, music, cadets, house competitions, and so forth. And to have all of those resources housed in a literal castle on a hill so close to Melbourne - amazing. If you have an interest or skill, MHS has a place for you. Not only a place, but a place for you to excel and enjoy.
Whichever you choose, I wish you the best. Honour the work.