"Highly educated parents,who also generally have higher incomes,tend to send their children to more expensive independent and Catholic schools or selective government schools,"they wrote."Such schools are then able to offer more professional development to teachers ... which in turn reduces the likelihood of teaching out-of-field."

Higher funding levels also meant schools could offer permanent employment contracts to teachers within their field. Schools on tighter budgets,however,were more likely to employ teachers on a daily basis where they often lacked qualifications for subjects they were asked to teach.

"Schools with more funding have a competitive advantage in the teacher labour market when recruiting teachers with the appropriate subject level qualifications,"the researchers wrote.

But AMSI schools program manager Janine Sprakel said better data was needed to explain why out-of-field teaching occurred,and that it was an issue across the country's school systems."It's true there are a range of factors. The issue is nobody collects the data,"she said.

She said Australia needed more maths and science teachers to fix the problem."In the short term we'd love to see really well-funded targeted professional learning that gives teachers the qualifications that fill the gaps. In the long term we need to attract more people generally into maths and science,and making that appealing in the minds of the public,"she said.