But thousands of NUT heads and staff remain resolved to walk out on Thursday in a move that will close many schools in England and Wales
When Anita Knight shuts and locks the gates of her south London primary school for Thursday's strike, she says it will be with a heavy heart.
As a member of the National Union of Teachers, and headteacher of the 460-pupil Woodmansterne Primary in Lambeth, south London, she plans to walk out with 22 of her staff.
The industrial action was not being taken lightly, she said: "Obviously people are going to be really inconvenienced by having their school close. But this is not something we want to do - I do this with a heavy heart."
Maintaining public confidence is the main challenge for striking teachers. The outgoing chief of the independent pay body for teachers has warned that next week's strike would damage teachers' reputations with parents.
Bill Cockburn, chairman of the School Teachers' Review Body (STRB) since 2002, told The TES that teachers risked losing the "great respect" they had earned over recent years.
He said: "The trouble about even saying you are going on strike is that it's like playing a game of snakes and ladders - and you have hit the biggest snake and you're back down."
Many teachers, pupils and parents will not know until next week whether their schools will be shut down by the strike.
About two-thirds of the 25,000 schools in England and Wales will return from their spring breaks on Monday, including almost all London schools.
Headteachers will need to determine how many of their staff will be striking, and prepare a risk assessment to decide whether they are able to remain open.
Few secondaries are expected to close, but significant numbers of primary schools, especially if they are smaller or are in London, may be affected.
The strike is in protest at the government's announcement of a 2.45 per cent pay rise this year, followed by 2.3 per cent in 2009 and 2010.
Mr Cockburn, who is leaving the STRB to take responsibility for MPs' pay, said teachers had not been short-changed.
The Government had planned to cap all public sector pay rises at 2 per cent, but the review body successfully secured a higher figure for teaching staff
The strike was "ill-conceived", Mr Cockburn said. "There's a general perception that teachers have a good deal."
But striking teachers believe they will win the support of parents and the wider public.
Sue Fielden, headteacher of the 420-pupil Torrisholme Community Primary School near Lancaster, sent home letters before the spring break advising parents of the school's closure.
"I met a grandparent while I was out shopping who was totally supportive," said the NUT member. "I think we have given parents plenty of notice to arrange childcare, so there should be no problem."
Thousands of NUT members are expected to take part in 47 rallies around the country.
They will be joined by some of the 27,500 lecturers from the University and College Union who have balloted to strike on the same day, and 100,000 civil servants from the Public and Commercial Services Union, who will be striking over pay in 10 government departments, including the Home Office and the DVLA.
But it has become more difficult for unions to co-ordinate a national strike of all teachers, as they are no longer negotiating with just one employer over pay.
Only six out of 83 academies have been balloted by the NUT on the strike, as separate pay negotiations with the majority of the semi-independent state schools have not yet been completed.
An estimated 7,000 teachers now work in academies, but the Government wants another 400 schools to become academies.
John Dixon, the NUT's local action co-ordinator, said it would be unfair to ballot academy teachers on strike action when they were still in pay negotiations. "It does make things more complicated," he said.
Headteachers' associations say there are numerous schools, including those with high proportions of NUT teachers, where staff will not be striking.
The Association of School and College Leaders and the National Association of Head Teachers have urged their members to be tolerant of staff who go on strike.
Jim Knight, page 29.