You can even get 97+ without any Band 6s.
89 in Eng Adv, Math Ext 1, Math Ext 2, Phys and Chem would give around 97.2.
This is also a good reason why school ranks are not that effective. A school could get 500th but every student could have an ATAR above 97, since (unofficial) school ranks are based on the percentage of Band 6s.