If you hate school, the chances are you'll still hate doing photography at tech. I was the same and really don't do well in a regulated environment like schools. I went to Sydney Institute to study web design and struggled just as much as I did in school! The difference was I'd spent a few years out in the real world washing dishes and doing other shitty jobs, so I had a bit more incentive than I had when I was younger.
Another thing to remember is that these days you struggle to get a job shovelling the proverbial with your HSC
After your course when everyone is looking for work, unless your portfolio is streaks above the rest, people with their HSC will land the good jobs without you getting a look in.
My advice - stick with your HSC and improve your studying skills and then do the photog course. If it's going to take that long anyway, you could also consider Uni, but that will be even harder to stick with than Tafe.