Hey, that's the method i use for my study and i'm currently in y12
so what you do is basically this:
-print out/prepare syllabus and place it on the left side of you (it is important as you need to refer to it constantly. hsc will only ask you questions based upon your syllabus)
-open up your school textbook in front of you
-get a notepad/exercise book/5subject notebook (this is what i usually do, as i divide each topics in the note)
-additionally, refer to other people's dotpoint notes because sometimes it might be handy when you are experiencing difficulty with textbooks
1) read the syllabus dotpoint and understand what you'll need to be paying close attention to
2) read the textbook that contains relevant information of your syllabus <Here, do not try to understand the whole thing at once. read once and then try to highlight key words that are important. then re-read the relevant page and try to understand in depth as you go on>
3) write the heading of the dot point you are referring to, and try to regurgitate the information you've just read in your head
4) jot things down in dot point forms in a seperate piece of paper (this will be your rough guide)
5) refer back to the textbook and see if what you've written down corresponds to the textbook info.
6) write on your notebook etc
repeat this process for each dotpoint
but most importantly, make sure you are doing this every night, after school in order to increase efficiency
this doesn't sound like it would take much time but it really does take a lot of effort and time
good luck