Your school doesn't scale the marks. It depends on how the rest of your school performs in the hsc exams and how you perform. If your school assessment mark is about the same as your performance in the hsc it won't scale up. If your school assessment is higher than your performance in the hsc it may even scale down. Its too hard to try and guess how the scaling will work and just because a subject didn't scale doesn't mean they stuffed up or you got ripped off. Its too complex to try and guess so just be happy with your mark.