It all depends on your school I would say. Your HSC marks for each subject are calculated by taking your raw HSC mark in the exam and averaging that out with the mark that your rank got (so for example, in English Advanced the 21st best mark). This is done for each subject and all those marks are averaged out for your ATAR.
That being said your ATAR is largely undetermined yet. Do you think that the 21st mark in English will be 75-80? Completely depends on the capabilities of your peers and how well they are going to go. It sounds like you go to a fairly academic school given that you have a fairly low rank with high overall marks. It is definitely still worth trying in the HSC and I actually do think you can get an 80+ atar if you really try. Good luck and I hope that answers your question.
