You must improve these ranks considerably if you want to get 98+. Here are a few examples:
In 2010, my school was ranked 63. In 2011, my friend did the HSC and got 98.40 and he was ranked: 1st in Ancient & Legal, 2nd in SOR, 2nd in English Advanced, 10th in 2u Maths, 6th in 3u Maths & 1st in History Extension. When we did our HSC, my school dropped down from 63rd to like 79th or something.
By comparison, I was ranked 1st in English Adv + Eng Ext I, 2nd in Ancient & Legal, 1st in SOR, 8th in 2u maths and 20th in 3u maths. I got a 99+ ATAR. (But I did get 98/100 in Ancient and 49/50 in SOR).
If you're aiming for 98+, you need English, Modern and Extension History to be in the top 5. You MUST bring 2u maths into top 10 and Chem+Bio should be no more than 10-15.
Just remember, NEVER let anyone tell you what you can't do.