exactly, I know heaps of people in my grade that are like "I finished the exam and had 30 mins left" or in a 3 hr trial were like "I finished with an hour left", and I'm at a selective school too. Obviously they're fast, and they are pretty smart too; I usually finish a 3 hour exam with 15 mins left because I take my time and use it to think longer, maybe they just think faster and that's their usual rate of thinking. If they chose to leave early, it doesn't mean that they're not as bright or something or that they're not trying, stop being so judgemental and blaming them on pulling your cohort down. One of the people in my IPT class who was ranked last in internals left the HSC exam early and she still got a band 5. When you see people leaving, that's their wish and you shouldn't even care for their decision, it is their own loss or gain.
You don't have the right either to tell others (especially people lower ranked than you) to not leave the exam, what's the point of doing that? Who are you to tell them what to do? I wouldn't do it because it is showing off indirectly, telling those not to leave for your own benefit because it will drag the marks down, while also showcasing your authority because you think you have substantial marks that will be ruined by them. Don't winge about your cohort, if you wanted a better one nobody said you couldn't go into James Ruse. Sorry for the sarcasm, but you need to accept what you are dealt with and do your own best, irrespective of others. I'm sure if you were ranked near last in a subject, you wouldn't want to hear 'either work harder, or simply don't attend the exam at all if you're not going to try or even sit the whole thing' from anyone else. Your school wouldn't tell you to do that in the exam would they? Why should you as a student, feign care and tell that to others then.
anyways I'm saying there's no correlation between leaving early and pulling down the marks of the school. Because there isn't any. In any cohort there are bound to be people who aren't performing of the calibre of the top students, but that doesn't mean you can pick and point them out and accuse them of leaving early, because in any case they could be the ones sitting the exam for the full time. I don't see how their marks would affect you, if you look at the state rankings, lots of the people who are there are not necessarily from the top schools in NSW anyway, so you really shouldn't be complaining about your cohort dragging you down, being the whole reason for getting bad marks
the other day one of the people in our physics class was chatting to the teacher about cohorts and the HSC assessments. There's about 7 of us in the room, all of different rankings in relation to the average mark. This person in our physics class and cohort is very likely to be in the top 5 or so out of the 42 people who did physics in our year. The conversation was open and very audible. She said to the teacher (the conversation being about getting a band 5/6 in physics and marks required to get one) "but our year isn't really that good in physics anyway". I was offended by that comment when she said it, and I'm around the average mark as well (78), though I kept my feelings inside and kept my mouth shut. I was about to say "then you must be really smart then", because they way she worded it could easily be interpreted as 'our grade is pretty dumb/stupid to begin with, there's no hope for a band 6 for most of them', practically an indirect insult to everyone in the room who are nowhere near the bottom of the grade. Fortunately the teacher replied with "We'll see", because it is honest to say that the unexpected or surprises can happen with our cohort this year relative to other years in our school. Basically your opinions of others in the year can hurt them, even though they don't tell you that they are hurt. And what you say, even though you think is muted, can be the same thing and effect as if it was said literally.