In each state or territory, the Government Education Departments have their own job descriptions for different classification levels for laboratory positions. Independent schools usually follow a ‘Technical Support Award’ that usually specifies different levels of responsibilities or duties, however this does not usually detail the actual role description. Many times Independent schools may even design their own job description.
It may be more helpful for you to ask members of your state science education technician association for their input here. For contact details of the various state association contact details see: http://seta.edu.au/state-associations/ There is a document that has described a four level classification level that you may find helpful, see 2014 National Standards for School Laboratory Technicians (Note: this document is under review in 2017)