Orca33 Hii I'm in yr 12 also, and I did 3 & 4 Bio last year as higher study and got around the same sort of of score that u mentioned for all my bio SACs except for the Unit 4 SAC on Evolution which I got 91% on. (I had a lot of personal things going on last year which sadly got in the way of me doing as well as I wanted to on my SACs). Like what was mentioned above, and from what I've heard SAC scores don't really matter but ur rank does. Plus if u do really well on the exam u can still improve ur study score. I got a B or B+ on the exam from what I can remember and was able to get an over 30 study score.
I hope this helps a little. 🙂
Don't feel discouraged bc of one bad SAC score tho!! There will always be topics u like and those u don't which can effect how well u do, or sometimes personal things come up that might get in the way. This might happen and that's ok, even tho ik it sucks. This doesn't mean u don't know the content or can't improve, and I'm sure u'll do well going forward! I've uploaded some of my bio resources here on ATARNotes so if u like I can send the links to some here if u like.