Job satisfaction and class sizes are among the key issues preoccupying teachers as the campaign begins
Three out of 10 teachers are unhappy at work while 10 per cent are ambivalent about the job traditionally regarded as a vocation.
Widespread levels of dissatisfaction in schools - particularly among the older, more experienced staff - are revealed in a survey commissioned by the National Union of Teachers.
Fewer than half the teachers aged 45-plus who were interviewed by pollsters ICM Research were satisfied with their job compared to 65 per cent of 35 to 44-year-olds and 85 per cent of 22 to 34-year-olds.
A quarter of the older teachers could not agree that they enjoyed doing their job - and a similar number, perhaps not surprisingly, were upset by the Government's clampdown on early retirement deals.
The findings of the survey were dubbed a "devastating indictment" of past and current governments by Doug McAvoy, NUT general secretary.
"The Government has managed to lose the confidence of our most experienced teachers," he said. "There is a cliff to climb in terms of restoring that confidence.
"Teachers have identified across the board - not just NUT members - two critical solutions for a new government, increased funding and reduced class sizes."
The survey, which is based on 530 face-to-face interviews with teachers in primary and secondary schools, was conducted between February 3 and 14. Quotas were set for age, sex, school type and union membership, and results were weighted for age within sex and school type.
Its results identify three main areas of complaint in schools - constant changes, administration and disruptive pupils.
But they also show that morale is lowest among the older members of staff who felt the pressure most acutely. Almost six out of 10 teachers aged 45 or more complained that they had personally been affected during the past two years by the constant changes.
The corresponding figures for the 35 to 44-year-olds and 22 to 34-year-olds were 48 per cent and 38 per cent respectively.
Four out of 10 older teachers grumbled about the lack of support from Government and outside bodies while more than a third complained that there was too much political interference.
Overall, just one in 10 teachers aged 45-plus spoke of being satisfied in the job, while three out of 10 were fairly satisfied.
Levels of job satisfaction were highest among NUT members (65 per cent) and lowest among those from the Association of Teachers and Lecturers (55 per cent). The National Association of Schoolmasters Union of Women Teachers was in the middle of the two.
Despite taking the brunt of recent Government reforms and the introduction of league tables, the level of job satisfaction among primary teachers was higher (62 per cent) than among their secondary colleagues (58 per cent).