Dont apologise! Its very confusing.

I just looked up Education in Australia on wiki

For WA, the minimum age to start pre-primary is 4.6 -> so turning 5 by June 30 that year

The MAXIMUM age is 6.6 -> so turning 7 by June 30

If I was you Miss H I would get a copy of the relevant legislation in your state (start with your local member but you may just be ableto google it) becuase it sounds like you are well within your rights to keep her back 1 or even 2 years.