I've been thinking how busy im going to be next year, I've been thinking is it possible to maintain a part time/ casual job, hobbies, and good ranks next year?
Yr 11, you can still do lots of hobbies/part time job etc., I only reduced a tiny bit in mind way in yr 11 (I was doing 20 hrs of dance in yr 10 though, along with violin and other ECs as well) and in Yr 12, you can still maintain a balance though you may like to cut back your hours of ECs or the part time a bit to maintain the good ranks when people become more competitive.
In Yr11, I still was dancing 14 hrs a week at that point and doing comp season among lots of other ECs. Yr 12, I reduced my hours of dancing a fair bit-but even though I tried to make myself less busy, I was arguably busy in other ways as I went away for 5 weeks in the year (3 weeks overseas pre trials) and got super busy on charity committee/organising debating. But it was more spur stuff than a constant dance commitment etc.
Basically, be conscious of it, but seriously don't freak out too much in yr 11 as that's a testing ground so you'll know how to split your time in yr 12. Yr 11 enabled me to know I'd be too stressed to aim at another dance vocational(sitting Adv 2 would have been lots of work) or do the comps @ peak HSC times like July/Aug etc.
You can have a balance of everything in yr 11 and 12, but obviously in yr 12, your priority may be a bit more school orientated so a reduction in some things, but don't feel compelled to give things or everything up. Prioritize what's worth doing, having a release/something to aspire towards outside of pure academics is so, so, so helpful and actually helps you destress and be better academically without even realising
Most people with part times only work max 10-12 a week in yr 12, or take time off around 'peak times'. These people still have time to do some sport or whatever it is they like to do and achieve good marks. Yr 11, you could be doing more, if you manage it well.
Seriously in the past, there have been people on this site to get 99+ and lead a super balanced life with sport, hanging out with people what not. They were just smart about their time.