The prediction is based on the 28per cent of existing teachers who will be aged over 65 years in 11 years.

It comes on the back of the NSW Teachers Federation predicting 40 per cent of teachers in NSW are due to retire in the next six years.

But the department said it was working to ensure the territory would have enough teachers in coming years. ''The average age of the ACT public school teaching workforce has declined from 46 years [and] two months in 2000 to 42 years [and] nine months currently,'' a spokesman said.

''This compares extremely favourably with many other jurisdictions where the average age is almost 50 years.''

However, a national survey by the Australian Education Union earlier this year found it was also difficult to retain younger teachers in the profession.

The survey of more than 1700 public school teachers with one to three years' experience found almost half expected to leave the profession within 10 years.

Pay, workload, class sizes, and behaviour management were the main reasons public school teachers gave for wanting to leave.

The ACT department said that despite the overall predicted decline in teacher numbers, Canberra was faring better than most and was attracting a good number of younger teaching candidates.

''The ACT has recruited strongly from the university graduate pool and continues to do so,'' the spokesman said. ACT teachers were provided with more flexible working patterns to suit families, and more leave-without-pay options for teachers wanting to travel without losing their permanent position in the ACT public school system.

The ACT could also ''lay claim'' to recruiting potential teachers from non-teaching backgrounds.

''These include youth workers, psychologists, social and health workers, and IT support staff,'' he said. ''Most jurisdictions only recognise experience gained in teaching, which limits the pool of potential recruits and ignores the valuable experience that people in non-teaching careers can bring to schools.''

This year 250 new teachers would take up posts within ACT Public schools. The Department had also offered 100 temporary contracts to cover vacancies left by existing teachers on leave.

The ACT had received ''strong'' numbers of applications for the teaching posts with more than 900 received for the 250 places. The most difficult places to fill were ''highly specialised and technical subjects''. This was an issue in all jurisdictions in Australia.