I'm searching for a school in nsw and i need advice?

I'm looking for a school in nsw and I like PLC Sydney and Queenwood. Is it just me or christian private schools are so expensive not like catholic private schools? I don't know how much public school would cost. I have finished year 10 in indonesia, but in Aussie year 10 will be finished in around december. Can I apply to the school and enroll in year 10 term 3 or 4?