ACT teachers are working the second-longest hours among states and territories, according to the latest Australian Council for Education Research statistics, with national figures showing hours are on the increase across the country.
The Staff in Australia's Schools report, a national survey of more than 17,000 teachers and school leaders conducted from May to August 2013, was published on Saturday.
Primary teachers in ACT and NSW schools reported teaching 50.2 hour a week on average in 2013, the second longest in the country apart from South Australian primary teachers who were teaching 50.5 hours.
ACT secondary teachers reported teaching 49 hours a week, also the second-longest apart from NSW teachers who were teaching 49.4 hours on average in 2013.
Hours are also increasing at a national level. Primary school teachers said they spent about 47.9 hours per week at working on school-related activities in 2013, up from 45.8 hours in 2010.
Secondary teachers said they spent 47.6 hours per week working on average in 2013, up from 46 hours on average in 2010.
Australian Education Union ACT branch secretary Glenn Fowler said ACT Education Minister Joy Burch was dismissing the union's concerns about teachers' excessive workload, saying that the figures showed that teachers were "overworked and stressed".
He was worried the workload "may be driving talented teachers away from the profession".
A spokeswoman for Ms Burch said "it is important to note that this is a survey of all ACT teachers, not just those in our public schools".
She said the report showed teachers in independent schools were spending more hours on school-related activities than teachers in public and Catholic schools, bringing up the average.
The spokeswoman said teacher workload in the ACT was on par with other states and territories and said the government was in the midst of enterprise bargaining negotiations with teachers.
"ACT teachers do a great job and the government values their work," the spokeswoman said.
Meanwhile at a national level, the survey revealed that the problem of teachers working "out of area" - or teachers teaching without completing at least a second-year tertiary subject in the area - has not gone away.
The new report found about 40 per cent of secondary and 20 per cent of primary school principals had difficulties filling staff vacancies for specific subjects, which left many teachers working "out of area".
Apart from special needs, geography and vocational education and training teachers, secondary information and communication technology teachers were the most likely to be teaching out of their field.
In primary schools, just 57 per cent of teachers training children in ICT has studied a second year university subject in the area according to the report.
Only 16 per cent of secondary teachers nationwide said they had done tertiary study in computing, and 8per cent said they had been trained how to teach computing.
The report also revealed teachers are struggling to keep kids in line, with nearly half of new teachers saying they want assistance in dealing with unruly behaviour.
Federal Education Minister Christopher Pyne said the results "reinforce the importance of lifting teacher education across the country, currently the focus of the Australian Government's Teacher Education Ministerial Advisory Group, which will hand down its report later this year".
"While the report shows that we have a workforce overwhelmingly passionate about teaching our young people, it clearly shows that many of them feel under prepared when entering the classroom," Mr Pyne said.
The report found that the proportion of female teachers has increased despite long campaigns to increase the number of male teachers and found the average age of teachers was 43.8 for primary school and 45 for secondary teachers.