An ATAR involves more than just your personal ranking at school. Your school's ranking affects it as does the scaling of your marks and the combination of subjects you have chosen.
I did HSC in 2009. Got an ATAR >96 but most of my rankings at school weren't that impressive. Some of my subjects scaled up heaps, some scaled way down in the HSC (as in I was ranked 4th with a mark of 96 at school but received an HSC mark of 85)
If you want more specific and practical advice on how to get an ATAR>92 PM me. Can share some strategies with you that have little to do with rank and all to do with how you prepare.