New research shows that while demand for teachers will continue to grow as enrolments boom, fewer staff are working in public schools compared with 10 years ago, while more have turned to the independent system.

According to a state government report seen by The Sunday Age, the proportion of teachers in public schools has decreased from 65 per cent in 2001 to 62 per cent in 2010, while the proportion of teachers in independent schools has increased from 15 per cent to 18 per cent over the same period. Catholic school teachers have remained steady at 20 per cent.

The trend is consistent with the ongoing drift of students to private schools, where enrolments have grown at a faster rate than government-school enrolments over the past decade.

But the report could prove politically sensitive as state teachers wage an industrial battle with Premier Ted Baillieu for better wages and working conditions.

Australian Education Union state president Mary Bluett said there were several reasons why teachers were leaving public schools. For instance, federal funding had allowed independent schools to reduce class sizes and market themselves to parents, she said, while in public schools, ''frustration with never-ending contracts'' instead of full-time employment deterred many teachers from sticking around.

''Without that certainty between three and five years, many newer teachers are leaving the system,'' Ms Bluett said.

The figures are contained in the latest Teacher Supply and Demand Report, which provides a snapshot of how Victorian schools are faring. The report also reveals:

■About 19 per cent of public teachers are on fixed-term contracts.

■Almost one in 10 principals are having ''major'' problems filling vacancies.

■About 29 per cent of teachers are teaching in subjects for which they are not properly qualified, with maths, science, language and technology among the hardest subjects to staff.

■One quarter of the paid workforce took extended leave in 2010, amounting to 1.3 million days in leave.

Teaching Profession Minister Peter Hall said on many measures, the report showed improvements compared with previous years, meaning government initiatives to attract and retain teachers were having an impact. But he admitted ''there is still more work to do. We will continue to focus our efforts on raising standards in our schools and building a system where teachers, principals and support staff are recognised and rewarded for the crucial role they play in making this happen.''

■FTomazin@theage.com.au