Just to elaborate on what's been posted above ^^^^
I would recommend pursuing early entry and doing your best to achieve a good ATAR (and put yourself in the best position for offers). Personally, it was only at the end of year 12 that I knew I wanted to pursue Science so I didn't even consider taking Maths and Chemistry (which I don't at all regret as my skills at the time were in other areas).
However, I still received the following Science offers:
- Guaranteed entry for a Bachelor of Advanced Science @ UNSW
- Early entry for a Bachelor of Advanced Science @ Macquarie
- HSC True Rewards for Bachelor of Advanced Science @ Western Sydney
- Early entry Bachelor of Science @ UNE
I applied to all these schemes as I wasn't sure whether I'd be accepted. However, I've realised a lot of these unis have
assumed knowledge which differs from
prerequisites. Assumed knowledge means that you'd benefit from having taken that course and the lecturers will assume you have studied the course (meaning you'll have to work harder if you didn't) but you can still take the course if you didn't study these subjects. Prerequisites mean your entry to the course relies on you having studied the prescribed HSC/ equivalent subjects.
At the end of the day, if a course requires a prerequisite that you didn't like at HSC level, you probably won't decide to major in that subject. That being said, it's always a good idea to do your research, compare courses and remember that you still have a chance of getting in! Good luck!!