I found a Trove doc - New South Wales, Australia, Government Gazettes, 1853-1899 for Miss Margaret McGrath retiring from the Public Service Board as a teacher in 1899. She was teaching at Rhine Falls Public School out near the Snowy Mountains. This may not be our Margaret Ann (Beatrice) McGrath but I have made a few assumptions.
Hi Sandy - have just spotted your similar thread on the AUS board, but will add here, my earlier thoughts .

TROVE offers up just a few articles re: "Miss Margaret McGRATH - teacher."
My thoughts were that they all perhaps referred the same woman ?
"Sydney Morning Herald" - 20 May
1882 - p. 7 ... posted to Provisional School at Bowman's Creek [nearest populous place, Muswellbrook ?]
"SMH" - 9 April
1885 -p. 4 .... Provisional School at Brook's Creek. [Additional item same paper on 6 May 1885 - page 7 ... new public schools - Brook's Creek near Bungendore.
"SMH" - 22 February
1888 - ... to Provisional school at Monaro [formerly spelled as "Manaro" - location southern NSW, east of Snowy Mountains.]
[Note: All above would be too early for your Margaret ? ]
"Evening News" (NSW) - 28 February
1891 - p. 2 ... to Provisional School at Stony Pinch. [Location - about 190kms N/W of Sydney - nearest most populous place is Meriwa - 34 kms away.]
1899 - Retirement from Rhine Falls Public School.
~ Lu