The School Certificate has two components.
School based which results in Grades A - E for the Mandatory subjects and your electives. This is also where there is a record of 'experience' subjects - those that require a set number of hours of study over the 4 years from 7 - 10.
In addition there are the externally examined subjects which are English, Maths, Science, Australian History, Geography, Civics and Citizenship, and Computers.
These are the ones where you get the Bands - 1 - 6 (although I am not sure about Computers getting bands or just a mark).
Together the two components constitute the SC (like school assessments and HSC in Year 12).
I hardly even ask my students in Year 11 what Band they got in the external exam but more what grade they were given as I believe that gives a better indication of ability.