It depends on the competition and how other people do it. Cause, in the end, your marks are a rank as a percentage (top 10% etc) so if you do badly in something other people are likely to do badly too. But abstract reasoning in my opinion is the hardest to get high because everyone does amazing, so if you even get one or two questions wrong you can get screwed over. I got near the top 5% for math and near the top 10% overall for my HAST (Abstract Screwed me over) last year but Penrith had so many people trying out I got reserved. Also, people don't take this into account but make sure you put a lot of thought into the order you pick your schools, I would have easily made it into Sydney Technical but they only offered spots to people that put them first on their list even if they got less HAST scores than the people that put the school second. Also A Tip (I didn't use this): I was thinking after my writing test there were no specific forms they told me I had to write in eg essay, narrative, or discursive. So I could have easily written a poem, it would have been unique and would have taken less time but I don't know if It would be a good option, someone fact check me. But it would definitely separate you from others, to everyone that is not in year 9 or 10 and is doing HAST I would say you try a unique form of writing and see how you go cause 20 minutes is not a lot of time to write a good story or discursive. But in year 9 or 10 I wouldn't do this cause these are the last two tries you going to get.