The problem with teaching Asian languages [properly] in Australian schools is finding qualified teachers. Aussie students give people with bad English hell, so native speaking Asian language teachers are rare. I had to "team teach" with an Indonesian teacher for a while, just to control the class. That's not a staffing luxury too many schools can manage.
On the other hand, you have local teachers who studied the Asian language at uni, but aren't anywhere near native speaker competence.
Luckily there is a new breed who spend a year or two in the country [eg, Japan and the JET scheme] before graduating as teachers.
Unfortunately, capable Mandarin teachers are the rarest of all.