If the trend continues the Hunter and Central Coast region could lose up to one third of its teachers by 2012.

Information obtained by The Herald under the Freedom of Information Act shows the NSW Education Department lost 270 teachers from public schools to retirement in the Hunter and Central Coast in 2008.

The NSW Teachers Federation said the number was expected to double at the end of 2009 after the NSW Education Department finalises its new teacher salary agreement.

Many older teachers' superannuation pensions are tied to their final salary.

If the same numbers continue to leave, the Hunter and Central Coast region could lose between 1500 and 2000 teachers by 2012, between a quarter and a third of its teaching workforce.

It also equates to a loss of up to 80,000 years of combined experience.

It comes after a report by the NSW Auditor-General in February 2008 found 16,000 teachers in NSW would be eligible to retire by 2012 and 25,000 by 2016.

NSW Teachers Federation Hunter organiser Fred Dumbrell said 270 retirements in 2008 " was a bit up on normal".

"The majority of teachers would have put their retirement back because of the . . . salaries case," he said.

Mr Dumbrell said the Hunter region was likely to feel the effects of large-scale retirements because of the age profile of its teachers.

Many senior teachers finish their careers at in-demand coastal posts after accruing transfer points in their career.

Remote schools in the Upper Hunter could also feel the ripple effect because changes to the transfer system had reduced the incentive for younger teachers to teach in hard-to-staff schools, Mr Dumbrell said.

"There will also be significant issues about being able to attract experienced teachers to cover really demanding senior curriculums," Mr Dumbrell said.

Universities such as the University of Newcastle are offering extra places in teaching degrees because of the national shortage, however it may not solve the problem.

"Part of the problem is not only the ageing of the profession but many of the young people beginning in the profession last only three or four years before moving to higher paid careers," Mr Dumbrell said.

The NSW Auditor-General, Peter Achterstraat, said the Education Department had increased its focus on retaining knowledge and skills of staff and had moved to introduce phased retirement.