Hey, heatherrose!
I'm in the same boat with my extension mathematics exam. I scored 66% when I usually ace it (80-90), so I was a bit upset, especially when it was the trial exam. All I can say is keep your head up and become proactive with your exam results. Don't worry too much about it, because if only two people passed, then it was probably a hard exam (BOS considers this when aligning your final raw marks).
This is how I acknowledge my mistakes:
I start by redoing the exam (under exam conditions). I may have just had a terrible day (two exams, that day), so my performance doesn't necessarily reflect my actual abilities. This is also a way for me to keep in check to see if I am capable of doing the questions that I couldn't (66 vs 94 is a big difference). Thus, I know where I need to go and that's my starting point.
From here, I do practice examples of that particular topic (either from past papers, or from the textbook) and get it marked by a teacher or tutor. That way, I can see the preferred method of setting your work out. Talk to your teachers about seeking extra help (whether it be after school or lunch times); they won't mind, and they will be more than happy. This is the
being proactive with your learning.
After that, I just do past papers (HSC at this stage) and getting it marked by the teacher. This helps to see a common weakness that I will need to improve on in the coming weeks of HSC.
Good luck with your HSC! Remember that it's not about the marks, but your ranking against your cohort. BOSTES doesn't care about the raw marks themselves, but your overall rank and mark difference. So if a lot of people failed, then you don't need to worry. As long as you have a decent rank, you'll be all set.