The below is copied from the Building Code of Australia (BCA) 2014 Volume 1. While this clause (D2.24) appears to have come into being in the BCA 2013 the content was largely present in earlier versions in clause D2.16.
(Note that “Class 2” buildings are Residential Flat Buildings)
“D2.24 Protection of openable windows
(a) A window opening must be provided with protection, if the floor below the window is 2 m or more above the surface beneath in—
(i) a bedroom in a Class 2 or 3 building or Class 4 part of a building; or
(ii) a Class 9b early childhood centre.
(b) Where the lowest level of the window opening is less than 1.7 m above the floor, a window opening covered by (a) must comply with the following:
(i) The openable portion of the window must be protected with—
(A) a device capable of restricting the window opening; or
(B) a screen with secure fittings.
(ii) A device or screen required by (i) must—
(A) not permit a 125 mm sphere to pass through the window opening or screen; and
(B) resist an outward horizontal action of 250 N against the—
(aa) window restrained by a device; or
(bb) screen protecting the opening; and
(C) have a child resistant release mechanism if the screen or device is able to be removed, unlocked or overridden.
(c) A barrier with a height not less than 865 mm above the floor is required to an openable window—
(i) in addition to window protection, when a child resistant release mechanism is required by (b)(ii)(C); and
(ii) where the floor below the window is 4 m or more above the surface beneath if the window is not covered by (a).
(d) A barrier covered by (c) must not—
(i) permit a 125 mm sphere to pass through it; and
(ii) have any horizontal or near horizontal elements between 150 mm and 760 mm above the floor that facilitate climbing.”
I hope that this helps.