Don't know of any partcular schools in North Ryde - apart from Macquarie University - and I suspect that neither of your kids are quite ready to go there.
Cheltenham Girls High - is one of the best - but you have to live in the area - and there used to be a waiting list.
If Catholic - Loreto College, Normanhurst - for girls - a few suburbs to the north There's probably state schools and Catholic and other religion systemic schools around.
Catholic:
St Kevin's Eastwood:
Website:
http://www.stk.eastwood.syd.catholic.edu.au
Holy Spirit North Ryde:
Website:
http://hs.nryde.syd.catholic.edu.au
Sorry I'm not much use - I'm a kid-free zone, I'm afraid