Ok, so I did try out for the selective school exam for year 9, but did not get in... I could however tell you what to prepare for based on my experience.
Personally, I did attend a tutor and that enabled access to numerous resources and practice tests. Nevertheless, there are many resources on some ATAR notes discussions and selective school sites - so use these and practice under a time limit of 30 minutes.
This year the students did both narrative and persuasive pieces for writing (as per my belief) so search up random prompts and write one every week! - It's best to do it a lot of times - in order to store ideas in your head and become familiar with the process/structure.
For the other tests, all I can say is to complete practice exams!!! here's a link: https://www.oztests.com.au/vic-sel-free-resources/
Maths - Year 8/9 fundamentals and basic year 10 level knowledge
Reading Comprehension - It's like an advanced Reading PAT test so read lots!
Verbal - My tuition teacher told me to read the dictionary which I actually did but didn't help too much so maybe revise over year 9 spelling lists and familiarise yourself with prefixes/suffixes.
Numerical - I can't say much for this one so it is best to just do the practice tests - but here's a tip; don't always try to guess an answer and instead opt to seek out a pattern in certain questions🙂
there are a lot of YT videos that also go into depth.
Finally, do not stress about the amount of coverage you are supposed to have - definitely prep but take it easy and plan wisely. Use the upcoming December holidays to study well!
All the best.
Feel free to ask any questions, I'll try my best to answer as an ex-exam taker 🙂lol!