Kaatie said:
1st 2nd 3rd etc in subject awards, are they based on purely the hsc exam or internal assesments as well?
It is first determined by your external marks (HSC marks). If you get the same mark, they look into the internal assessment results.
Source:
http://www.boardofstudies.nsw.edu.au/ebos/static/TAINC_2007_12.php
The Top Achievers in a Course List includes the names and teaching schools of those students in each course who achieve Band 6 or Band E4, as appropriate, and are placed in the top group (see following table). They are ranked firstly by their HSC mark and secondly by the average of the examination mark and the moderated assessment awarded for the course. In the case of extension courses, marks awarded for other courses in the subject area are also taken into consideration.
HOWEVER, in my opinion, the above procedure may be different if you are from same school as suggested by few stats by some other members on this website.