That depends on which state of Australia you're in. When I grew up in the ACT, the school districts/zones are enforced -- ie. if you're in the catchment for that public school, you can only go there unless you pay for private school. It was a pain when we were living in new suburbs as a kid because when a new school opened and the districts were divided, you had to change schools to go to the new one.

In Victoria, where I live now, you can go to a school in a different district but they don't *have* to take you. So there are still some suburbs with great schools that people will move into (to be guaranteed their kid will be accepted there) but there's a lot more choice.