I don’t think it’s possible to get into CTHS unless one lives in their catchment area and real estate in that area is pretty expensive. I have a relative who deliberately looked for a place in their catchment area but they wanted to live in a suburb like Cherrybrook anyway so they weren’t just spending a fortune on a house for the sake of getting into the school. I‘ve heard good things about SMSH from a couple of their graduated students, but also know of two students who found that the extra commute (total of nearly three hours a day) wasn’t worth their time and they returned to our local school after less than a term.
Thank you for adding this information about CTHS. Of course, the suggestion is based on the event where the student lives in the school's catchment area. If not, then CTHS will definitely not be an option. With SMSHS, the suggestion does not take into account students that have to travel significant distances and for long periods of time each day to get the school. Similarly to CTHS, the suggestion should be taken into consideration if the student lives close to the area where the school is located. As a former SMSHS student, getting to the school wasn't much of a problem, having to catch a 3-minute train and then a 5-minute walk from the station to the school. If OP lives far from the school (similar to the examples of past students that you've mentioned), then SMSHS will likely not be an option either.
Lol problem is i dont rlly want to transfer from a partial to a partial bc I dont want to go thru the trouble of applying for it. I just want to go to a comprehensive that offers many opportunities(fairvale does amc and debating comps, my school does none of these), then dip to the high tier selective school.


Also fairvale offers an accelerated math program.
Both the schools I mentioned are comprehensive and the suggestion to apply to and enrol at either one of them is based on the eventuality where you don't make it into your chosen high tier selective school. I was not suggesting that you should enrol at either of those schools and then apply to the selective school.
Also the rank is 305 for st Mary’s which is like nearly double my current one

Rank is not always a good measure to assess a student's potential performance, particularly when considering a school like SMSHS, with historically fluctuating ranks. When I graduated from SMSHS in 2019, the school was ranked 208th, which is significantly higher than FHS's 2019 rank (340). It is also worth mentioning that SMSHS's 2020 rank is still better than that of FHS (359).
Back to the main point, SMSHS is a school that accepts students of different academic backgrounds/capabilities, as long as they can prove to the school that they are a committed student, not necessarily in an academic way (although that would be favourable), it could also be through their involvement in extracurricular activities and such. The rank will thus fluctuate each year considering the differing abilities of the school's cohort each year. Keep in mind that SMSHS's year 12 cohort is a large one, with about 400-450 students, each of which has unique capabilities, academic or otherwise. It is important to mention that this is a school where you can achieve a high ATAR (the school is not new to 99+ ATAR's and state ranks), provided you are determined and are putting in consistent effort throughout your time at the school.