I just graduated from school at geraldton, western australia.
And i can tell you, you will be welcome with open arms to teach, as they seemed to always be struggling to get teachers there. Obviously Geraldton is where your wanting to go? So thats a good start on your behalf.
My best suggestion, find where you want to live, i.e geraldton. And if you still wanting to be a physics teacher, simply search for the schools in Geraldton.
www.geraldtongrammarschool.com.au
web.ncc.wa.edu.au/etc..
Make some phone calls, and openly discuss your interests, and query how the 457visa works. Usually the Employer does all the hard work of getting you over here. And they will Know
Exactly how it works for you to work here, rather than asking a bunch of windsurfers that will be mostly guessing on how it works..
Goodluck