It is possible but it will be tough, I started it a month back and there's a project in it which you'd really want to be doing asap. I do highly recommend the Revise Wise revison book on it because it has everything and then just do all exam papers on Studiclix. You will need an Ag Teacher to sign off your project so you should try see if there's a teacher around to do that for you. Another good option would to find a grinds teacher to help you.
only do it if you really need it very risky on your other subjects starting now. go to an ag science or biology tecaher and there advise you best. make sure you have a book or go to an revison course in a grinds collage to get notes and them courses would u make you aware of shorcuts etc