*Ninny-mole* said:
I'll also be an idiot if I go in there and get less than 10% despite 2 years of hard work in the subject.
Seriously, at least attempt the paper. Going in there and getting 10% is better than the non-attempt you will recieve on your HSC if you don't go. I was in a similar situation with the mathematics paper. I had to decide whether to sit the exam and be lucky to get 10% or not to sit it at all. I refused to do it and wouldn't listen to my teachers because after putting in so much effort I didn't want to get such horrible marks, but changed my mind half an hour before the exam. I'm so glad I did. I went in without knowing half the course and knowing I wouldn't be able to physically complete even the parts I knew because of health problems, but I realised a crappy mark is better than nothing. I stressed out, wrote hardly anything and came out of the exam wishing I'd run away and destroyed my paper so no one could marks it, but now I'm happy I tried.
I know it's a different situation but really its better to be able to say you went in there and gave it your best shot, rather than just giving up when you're so close to completing the subject. You put in all that effort and you at least deserve to get the piece of paper saying you completeled 3 unit maths, which looks good on its own. The marks you get aren't the end of the world, its the fact you finished the course! Teachers are right about these things sometimes, I basically just repeated the advice everyone gave me (the advice I wouldn't listen to)
Only you can decide though, but just make sure you're really sure about your decision because there's no going back. good luck tomorrow