This is an undated sketch of Croydon Public School in Sydney. The text underneath reads:
"CROYDON represents a 2nd class school of three departments, accommodating between 400 and 600 pupils. This building is constructed of brick with stone dressings. Cost £5,463."
The school opened in 1884 and the fashion seen here - the sailor suit and straw hats, the women's outfits - indicates the sketch might be from the 1890s / early 1900s.
Information on the the Croydon P.S website suggests the sketch may be from an 1890 set of drawings:
"The Department's Architect, William Kemp, was asked for a sketch plan of suitable buildings in July 1881... Kemp's plan was approved, but unfortunately neither it nor the full plans which were completed in July 1882 have survived. However, Kemp used Croydon as an example of fine schools built by the Department when prepared a set of plans and drawings for the Minister's report for 1890."
Some school sketches have survived in the partially digitised series of NRS 15051 Department of Education Photographic Collection.
Image ID: NRS-15051-1-10--9