Stay. Do not move. It will be a bad idea.
1. The only reason why moving to a selective school is a good move is because it sets a studious and serious mood amongst your peers, and this allows you to prioritise studying as number one. However, since you are already self-motivated and are already doing well in your current school, the academic competitiveness that is meant to drive you is useless. In my opinion you will either perform the same or better at your current school as you're comfortable with your vicinity. Who knows what problems you might encounter at your new school.
2. No. The first 2 weeks of prelim are very easy to catch up to.
3. I will speak from my experience. I also moved to a selective school for Yr11. I went from taking 10 minutes to walk to school to taking over an hour to get to the selective school. Unless you're a morning person, you're going to find it difficult to adjust. By travelling for an hour to a selective school you'll feel much more tired everyday and also lose time in the afternoon to study/relax. And nope, no one ever studies on the train unless it's for an exam.
4. No. Just come first for everything and you'll be set.
1. That's not the only reason to move, next post gives a situation that explains that. Though in extremely rare occasions you may get a Godlike cohorts like some selective schools, then there won't be much reason in moving. (Though that would be fairly difficult to assess)
2. Ok.
3. I travelled 1 hour+ just to get to a 400+ school since like early July during the HSC, personally i adjusted fairly fine waking up at 6:30 am, though then again, there was not much point in going to school anyway for me lol. Yer i can't study at all on a train, it's useless and crowded, and the junior St George Girls are bloody loud as hell(no offence to any here.) Then you have to switch trains again, where there's nowhere to sit. Then you come home really tired, then sleep for approximately 1-2 hours.
4. Not that easy of a thing to achieve depending on your situation/ if there's at least some high achieving people in your cohort and even then you can't rely on them achieving legendary results in the HSC, since they may do worse than you expected which will drag you down if your not first in terms of your moderated assessment marks.
High 300's is a LOT more than "isn't great" to be honest. How are you ranked relative to your peers at your current school? If your not near the top then moving to a good selective could make a big difference on your HSC. And maybe have a think about what degree (and entry ATAR) you want to do, then evaluate whether it's worth the big change.
Pretty much this yer. I was just gunning for atleast 95 to get into my degree, so i wasn't aiming extremely high (99+) from the beginning and my effort into my HSC was not that great but i still got 97.80, didn't come 1st for any subjects so do as above has just said.
Another thing, there may be some biased marking in lower ranked schools, and may have a different standard to the HSC marking, so it's a more reliable assessment of how well you'll do in the HSC in higher ranked schools depending on teachers.