Whhut i though Balwyn is like one of the top performing state schools (non selective) in the state?
School hasn't even started so there's definitely time improve
Don't stress. Methods takes practise. You need to be patient as amazing results don't magically appear the next day.
Math is a skill that needs to be exercised regularly. So don't do nothing one week and cram the next. You need to consistent with your study.
How to get better? Do questions. Expose yourself to different questions, and make sure you understand the theory and concepts behind it.
Do the questions in your textbook and don't beat yourself if you get it wrong or don't understand. Make an effort to understand questions you don't. You need to address your weaknesses head on. How to do this? Ask your teacher/ tutor or here on AN....
You say you are weak in your foundations... Take a look at 1/2 and you do some questions that you have trouble with. (DW about probability; 3/4 is totally different) Take a look at Linear,quadratic, cubic algebra and graphing. Might want to do some exercises to algebraic manipulation and expanding and factorising.
Take each day as it comes and work towards improvement, you if work diligently from early on you will put yourself in the best position come exam time.
Best of luck.