like everyone said 100 in every subject is quite unrealistic ( though im sure for most of us that is the ultimate dream
) but regardless all u have to aim to do is better than most of the people who do ur course. the atar is a rank right ? so its not about what mark u get ( though that makes all the difference ) its about where that mark puts u.
i think u should put aside all this marking/ranking bs ( because clearly its making u upset thinking ur ranks are bad, and thats the best way to lost motivation, by thinking ur already disadvantaged) and just focus these next 8 weeks on studying and covering all ur weaknesses.
study smart not hard, u dont have much time left, but definitely enough to make a difference. u go to a very good school, the standards there are very high, you have a better chance of getting there than most of the kids sitting the hsc, plus u have a goal, now just go and study study study ! HSC is 50% ofcourse u can still get a 95+ uai if u put in ur all from now on!
its a little like that quote ( though its a little corny ) "
aim for the moon, because even if u miss youll land among the stars " hehe aww.
btw sorry my grammar is atrocious im aware, im just really lazy to write all proper on the net ( & im sleepy lol ). as long as u understand what im saying