Homeschool is legal in every state/territory in Australia. In general, the requirements are:

The parent who will provide the education:
1. Submits an application to their state Homeschool office.
2. Submits a plan outlining the education to be provided to show they are meeting the subject and/or syllabus requirements for their state. In some states (NSW, ACT and WA) this plan is shown during an interview.
Children between the ages of 5 or 6 and 17 must be registered (this age varies slightly between states).
In some states, there is a meeting between the parent and a representative of the registration body.
In most states, there is a periodic review of your child’s progress and ongoing plans.
In some states, you are required to report on your child's progress.