In wa, they start kindergarten if they are 4 by end of june but some are turning 5 after june if that makes sense.
Pre primary is five before end of june and then some turn 6 after june. PP will be compulsary next year. Kindy not, but is rare that kids don't attend. Kindys are attached to schools now unless you go with a community kindy or one through day care.
here is a wa calculator:
hope I am allowed to put the link in?!