things must be different here in WA, kindyand pre primary are part of the schools. Kindy > pre primary > year one. all are compulsory cept kindy after next year. I've never really understood why you wouldn't send your child but I guess its all personal preference.
my dd missed out on a great portion of pre primary and by the time she got to year one she was so far behind what was expected of her. I think kindy and pre primary are really important