Regardless of what specific marks you get, you should be working equally hard if not more in your school assessments as well as your external assessments. If they are both significantly different (after being moderated) then it would affect your overall ranking. The more people you beat, the more likely your UAI would rise.
After marks have been moderated in accordance to rankings and examination marks, if your combined HSC mark is the same as one from another school, you would not be disadvantaged nor would that person be at an advantage for that course. If you have the same mdoerated assessment mark as someone else, then the external examination would determine the final rankings.
For an individual school, if the school's assessment average is higher than the school's examination average then the assessment marks are likely to be pulled down. If the school's assessment average is lower than than the school's examination average then the assessment marks are likely to be pulled up.
So basically moderating takes care of any disadvantages or advantages other schools may have over others. If assessment marks are too high overall compared to the examination mark, then they'll be reduced. If assessments marks are too low overall compared to the examination mark, then they'll be increased. Moderating heavily depends on the school's performance in the external examination.
Remember, the more people you beat the higher your UAI is likely to be. Your school probably wants you to help each other to try to maximise everyone's UAI. Ranking matters when trying to calculate the UAI.
