Almost all student visa holders are required to maintain a specific type of health insurance known as Overseas Student Health Cover. The exceptions are for students from Sweden who have insurance provided by CSN International or Kammarkkollegiet, Norwegian students who are covered by the National Insurance Scheme and Belgian students. You can find out more about visa conditions on our website at www.immi.gov.au/students/visa-conditions.htm.
According to this website, all students in Australia who have come from overseas must have a health insurance policy while they are here. It is very important you maintain this health insurance for the whole time you are on a student visa— not just while you are studying. Your insurance must commence from the date you arrive in Australia and remain in effect until you leave, or move to a different visa subclass
An Overseas Student Health Cover will cover you for some specialist services and medical emergencies. However, you may need to pay for certain treatments. You should understand the details of what your policy covers before travelling to Australia. If you are unsure or cannot understand your policy, you should contact your health insurance provider.
– According to the Australian Government Immigration Blog