Once upon a time, Sydney families did not angst about where to send their children to school. If they wanted public education, they chose the local one.
But due to policy shifts over the past few decades, parents now feel they have a right to choose their child's school. Some base their choice on NAPLAN results, some base it on a school's reputation, some base it on the socio-economic status of its students.
Some base it on practical considerations, too. Families might choose a school that's on their way to work, or close to grandma, or has subject offerings that appeal to their child, like a dance program or a school newspaper.
Choice is good for the families that know how to exercise it, but bad for the system.