Students will generally have to write their programs to handle a wide range of input data. There final codes should be emailed to a central marking facility, where members of the jury will test programs for functionality and speed against a set of standard test data which they have designed. Marking is therefore generally performed automatically, and hence objectively, by a marking program together with test data. The top students will receive invitations to attend a training camp, where formal teaching will take place and further assessment will lead to the selection of an Australian team. There is no national program for teaching Informatics in Australian Schools.
Some instruction takes place, especially in some states.
For example I have become aware of some programs in certain Melbourne schools. There is of course now a national policy for the teaching of some established subjects like mathematics in Australian schools. As a mathematician myself, with considerable experience teaching in an Engineering Faculty, I can not claim that any of the national curriculum is expendible. I do think that there can be some over-emphasis on the teaching of Calculus, but principally when this teaching leads to mechanical knowledge of Calculus rather than an understanding of how Calculus works. There have been many changes in the mathematics syllabus in the last two decades.