just thought I'd pop a note to let you know that I just finished doing my HSC at TAFE, and it was good! I worked much better in that sort of environment than I did at high school, and performed better as well. It's alot more informal - you're on a first name basis with all the teachers, and your schedule may work out to be pretty random, but it's good. Generally, it's pretty easy to learn there because alot of people are there under similar circumstances as each other (having dropped out or whatever), and are pretty focussed, so you don't get as distracted during classes.
I dropped out of high school half way through year 12, and spent 2 years at TAFE doing my HSC. I did 3 subjects (preliminary and HSC) in the first year, and 3 new subjects this year.. which is a pretty good option if you're working or something as well, because there's alot more time to devote to individual subjects (and I only had to be there 3 days a week). I also did a subject through OTEN which I wouldn't recommend unless you're HUGELY motivated.. it's really hard to get your arse into gear.
Anyway, check out their website and find out what classes your nearest TAFE runs. I was at Hornsby and they had English standard, advanced, extension 1 and fundamentals.. General, 2U and 3U maths, economics, modern and ancient history, physics, chem, bio, senior science, art, IT VET, business studies, software.. and I think that's it, but yeah, pretty good selection!
Give it a try.. it worked well for me, and everyone I know who's done it really loved it so good luck!