Decent girls public schools in Sydney?

We've been living in the inner west but now that we have 2 young girls we are thinking about moving.  we need more space and are keen to find decent public girls schools (cant really afford private).  Have looked at Willoughby GHS but that area is quite expensive.  Anyone know what its like up in Wahroonga, St Ives or nearby?  Would prefer something on the train line, but open to any ideas.  Appreciate any knowledge regarding school zones and where the boundaries cut off at?

Regards

Wahroonga and St ives more expensive than Willoughby!
Could look at McKellar girls mackellargirls.nsw.edu.au
or have you thought about Catholic girls high schools there are lots of them!