I ranked 1st in eco at my top 10 school in Year 11. I'd say that if you're passionate about eco, it's definitely possible to self-learn most of the Year 11 content using resources such as the Pearson and Riley textbooks. However, even if you think you understand the content, be careful because you need to be able to apply it too. One of the hardest parts of the course is essay writing, which requires you to have a holistic grasp of singular dot points and also know a lot of real-world context such as stats, government policies, trends, etc. Also, ensure that you know how to draw all graphs, which you'll need in your toolkit. Year 11 is meant to be pretty basic, but since you're new to eco you really need to take some time to really absorb everything and gain a solid foundation for the Year 12 content.
I think it would be sufficient to be a little ahead of your school's schedule and get through any remaining Year 11 content during the term 2-3 holidays or until a few weeks before prelim exams. Spam past papers before prelims. In the holidays before the HSC starts, get through the first term of HSC content. For most schools, the first exam will be the Brazil case study, which really doesn't benefit from starting very early. Check with your teacher about what topic you'll be doing first.
The summer holidays are the best time to get ahead for the HSC. You have 6+ weeks to study the next 3 topics. It's not too late to wait until then to grind for eco and maximise your chances of doing well in the HSC. At least, that's how I feel because it's what I've been doing these holidays.
Good luck with eco! It's a great subject
