Same thing here, I subscribed to this thread as I want to know more.
From the different threads I read in this forum Onslow and Tawa seem to be good options rather than Newlands.
We would like a public school and have option for IB or CIE but public schools that accept girls do not offer IB or CIE (only boys can have CIE at wellington College from what I saw....), so if we stick to Public Schools and have girls then we have no other choice than NCEA which is also recognized for studies abroad so that should be fine.
So now we are hesitating between Onslow and Tawa and our two girls will arrive by year end 2017 to start college and high school 1st february 2018.
It's really hard to decide...
So if anyone arrives earlier than us and can update this thread with their fresh experience with Onslow or Tawa or Newlands, that would be really great

Thanks in advance