listening to classical music only helps you get into the desired attitude for taking in new knowledge. That is only if you enjoy listening to them.
But if you want to concentrate on your studies, you really need to do a serious mind adjustment especially for those year 11 & 12 students. Most kids without a family mentor like their own father or mother would tend to underestimate this. By the end of year 10, you should start building your passion for study. One good way is to start seeking your interests, engineering, medicine, law, business, etc. Just go through websites relating to these branch of professions. This is only one of the way for you to start feeding your hunger for knowledge.
Study techniques after all these years of experience like many other uni students made me realise that it is not one of but the essential element for your concentration and ultimate success.
Personally, I hate text book readings but that's the only way for a solid and secure learning of all the theories. One way I do it is to carefully go through all the topic objectives and glossaries as they tend to give you an overview of what's ahead. It doesn't matter if you don't understand them a first, infact, it's better if you don't because that will just trigger your curiousity for that particular section of topic. So when you do actually go through the theory content, you're ready to accept the knowledge the book is feeding you while you're reading it.
Lastly, it really doesn't matter if you were a bad or good student in junior high or middle high school. Anybody can achieve great results if you make a good use of your time for the last two years. Well, not literally.