The only main advantage in this system is you can link year 11 and year 12 content very easily and possibly can better accommodate those who want to do accelerated courses. However, there are many more disadvantages to this system than advantages such as for maths-you will need to revise over content learnt in the previous year if you do it in year 11-which is an absolute pain-because maths is a subject that has to be practiced every day/week, and also the speed of learning the content would be quite fast paced which means if you don't understand anything and if you don't grasp it immediately, you will be behind, and I think the most significant disadvantage is that your school is only one of the very few schools who does this-and you are competing with students who have adopted gradual understanding over two years-which usually means better results-unless of course, your school and yourself are really bright students and find the normal learning pace too slow.
I think this system is extremely problematic for subjects like English-because whether you do it in year 11 or year 12-you will be disadvantaged-you will not have as much time to practice on the knowledge you really need-waste half a year doing preliminary stuff not counted towards HSC-and not enough time to refine your skills-4 modules in 2 terms is seriously very very intense, and imagine trying to recall information learnt a year before in the HSC...
Top 3 tips to ace your subjects
1)Know what subjects you are doing in year 11-and find preliminary and HSC textbooks on it-and read it thoroughly in holidays-understand as much concepts as possible and perhaps even try to do some practice problems whilst checking your answers-and MORE IMPORTANTLY, CIRCLE ANY CONCEPTS YOU DON'T UNDERSTAND TO ASK THE TEACHER IN THE COMING YEAR and also circle questions you don't know how to do after several attempts to ask the teacher as well
2)Make sure you stay on top of your notes and assignments and assessments-maybe even start try to do a basic set of notes from textbook information and syllabus before the term starts for the upcoming one-two topic, if you are doing English-read all your English text before hand and find related text for any modules that need one
3)Maintain an optimistic attitude, never give up-keep trying hard and put consistent effort in -as long as you put in the effort-that is the best way to ace your subjects
I seriously wish you the best of luck for acing your subjects in your preliminary and HSC years
Probably the most important tip is to CONSISTENTLY revise over content you have learnt-particularly during your year 12-summer holiday-use that to revise over all concepts learnt in year 11 subjects(those 3 subjects you also have to do HSC for), with as much consistent revision as possible-they will be stored in your long term memory-but still practice it when you have time. Hope this advice helped