You gotta have really good stuff in your application because the results dont even matter. I tried out for mhs year 10 entry and I had stuff like regional soccer (one level below state) and cricket, robotics, chess and a bunch of other stuff. Still didnt make it in lolololol.
Youll need to have very strong extra curriculars to make it in. I think debating and cadets are things they really like.
For Mcrob your chances will be very slim, as they will be choosing only a couple of people depending on how many leave that year. so there may be no spots as well.
MHS has a minimum of 28 students that can enter, and also some more depending on how many people leave that particular year.
Good luck though!
by the way the year 10 exam is much easier than the year 9 so you dont have to even stress that much.