What's the salary of teachers in public schools?No!
When we talk about Selective Schools, we usually have the public high schools in mind.
Sydney Grammar is selective, but is a PRIVATE school. So can afford to pay its teachers more.
I don't know anything about double pay. I've never been a school teacher, but I know some better off private schools may pay their teachers about 15% - 25% more than their public school counterparts. This way they are able to poach talents from the public sector. Like in the commercial world; if you think someone is really good, you're prepared to pay him/her heaps to lure him/her away.