i might be shooting myself in the foot with this, but for maths students i make this comment
i don't want you guys to accuse me of leading you up the garden path with these papers, and by extension all the older stuff on nesa and thsc websites
but taking advise from the 2 students who topped the state in 2023 for maths ext. 1 and 2 who were asked how they did so well, they both said exposure to maths comps and olympiad stuff made it easier to tackle the more challenging questions, and that catapulted them to 1st place
so although it may seem to be a little off-topic, nevertheless i refer you to the aops website
https://artofproblemsolving.com/community which has an enormous amount of such material
if you don't have time at this stage to embark on such an adventure, i would recommend the bos trials and entwistle trials which goes a long way towards such exposure, but in much less time
i know some dudes on the hsc exam committee and in a coy non-committal sort of way they kind of agreed with me