Some schools in Australia have developed strong reputations for teaching languages to their students. They have developed methods of teaching their students based on an immersion method. This approach is where part (often around half) of the curriculum is taught in one language, and the other half in English. Teachers are often designated as being an 'English' teacher or an 'other language' teacher. So for example, at a school where Italian is taught, some teachers would only speak to the children in Italian, while some would only speak in English.
Often subject areas are taught in a designated language, so Physical Education and Health and Art might be taught in English, while Science and Math might be taught in Italian (or whatever language is the focus of the school).
These schools require highly specialized and skilled teachers, who are able to offer both subject matter expertise in their teaching areas, as well as a high level of language teaching skill in their chosen language.