The number of hours a technician is employed in a school science area is a school based decision. Some jurisdictions may have a formula that they use to determine the staffing allocation.
A 2009 report found that there is great variability across Australian schools regarding the level of technician staffing. The report considered a level of servicing recommended by the UK Association for Science Education based upon a servicing factor. This report, as well as the Laboratory Technicians Association of Victoria (LTAV) and Science Education Technicians Australia (SETA), recommend that a minimum standard should be established for a service factor of at least 0.6.
Note: The service factor is calculated by dividing the number of technician hours per week by the hours of science teaching per week.
The UK ASE has produced some guidance on this topic that you may find helpful: Best Practice Guidance: Technicians (This document is no longer available as of July 2018).
Association for Science Education. 2017. Best Practice Guidance. Guidance on Science Technicians. https://www.ase.org.uk/documents/best-practice-guidance-technicians/best... (This document no longer available as of July 2018)
Hackling, M. 2009 ‘The Status of School Science Laboratory Technicians in Australian Secondary Schools’ http://seta.edu.au/wp-content/uploads/2016/04/National_survey_results_09.pdf (Accessed August 2017)
LTAV, 2012. Technical Staff in Schools, staffing and conditions. Policy Statement. https://www.ltav.org.au/policies/ (Accessed August 2017)
SETA, 2014. School Science Laboratory Technicians National Standards for Professional Practice 2014. http://seta.edu.au/wp-content/uploads/2016/06/2014-School-Science-Laboratory-Technicians-Standards.pdf (Accessed August 2017)