As a holder of a student visa, you (and your dependent family members), are entitled to work in Australia. Please see information about working while studying and University semester dates where you can also find information in .pdf format which you can print off for your employer.
Please note, the Department of Home Affairs considers your course to be 'in session' for the duration of the published semester dates, including examination periods.
For further details regarding work rights see condition 8105 at the Department of Home Affairs.