ok, for school assessments, if a selective student get a same mark as a normal school school student, then the selective student gets scaling advantage. this is bcause standards in different schools are differnt. selective students may be working harder, or do harder exams etc etc.
For hsc exams, depends on how well the school group goes, students in the school gets scaled accordingly. obviously, those top selective students get good scaling advantage. i reckon it is fair for people to get advantage since they could bother getting into those selective schools
also with the hsc, it is very hard to 'bomb out' since u can claim sickness or misadvanture, in which they look at your school mark more that your 'sick hsc' mark