Your final HSC marks is the average of your scaled exam mark and your aligned internal mark. So no matter what you get your exam mark. It also affects your internal mark in how it is scaled. How much by will depend on how the rest of your grade goes (not just the 5 extension kids, surely there are some other reasonably good kids), and how close you are from rank 1. If rank 1 is way ahead of everyone else then your aligned assessment (internal mark) won't be affected that much, assuming your mark is the number 1 mark. But say you're only a few marks back that it will have significantly more impact.
Really though, you want everyone in your grade to ace the exam as well, because then you will be scaled up more. You don't want to be the only one who gets 100-105+.
Also the Gosford High trial was the independant schools trial, which was pretty easy this year. Just random fact for person above.
