Cramming works sometimes but not all the time.
For my trials i crammed for SAC, in the 40 mins between my modern exam and SAC and i got my worst mark yet and it meant i ended up coming equal first, which stuffs up my internal mark.
Plus it doesn't work incase you get sick or something, my friend my cramming buddy got sick during her trials, then she had to do all her exams in a week, stuffing up her cramming technique.
So kiddies starting yr12, cramming works but don't rely on it. One hour of effective study from today till your HSC will get you better results.