Anger over the Government's pay policy exploded today when up to 400,000 teachers, lecturers, civil and public servants went on strike, disrupting thousands of schools, colleges, jobcentres and Whitehall departments.
Teachers swapped the classroom for the streets as they took part in scores of rallies and marches to protest about below inflation wage rises and warn of a "serious downturn" in recruitment.
Schools Secretary Ed Balls visited a school where teachers continued to work, and claimed parents as well as other teachers were "annoyed and disappointed" at the action.
But the National Union of Teachers said it had caught the mood of its members, adding that support for the stoppage had exceeded its expectations.
One estimate tonight said the strike had closed or partially affected up to 9,500 schools, affecting up to 2.9 million children.
Teachers who mounted picket lines outside schools said they received support from parents and other workers, while those attending rallies attacked the Government for saddling them with debts then awarding below inflation pay rises.
Up to 7,000 joined a march in central London, carrying banners describing the Prime Minister as a "clown" and warning that the Government was trying to "wreck" the education system.
Gordon Brown described the strike as "unjustifiable", but he was urged by the NUT to halt the "downward spiral" in teachers' pay.
One in three schools in England and Wales were closed or partially shut, with up to 90 per cent of schools affected in some areas.
Christine Blower, acting general secretary of the NUT, said union membership had increased as a result of the dispute, adding that teachers' pay was now on a "downward spiral" after decent increases when Labour returned to power in 1997.
TUC general secretary Brendan Barber told the London rally that giving public sector workers below inflation pay rises "simply wasn't good enough" for a Labour Government, adding: "We need a fundamental change of direction. If the Government continues to use the public sector like a political football, I am convinced they will pay a devastating price at the general election."
Sally Hunt, general secretary of the University and College Union, whose members also went on strike over pay, said education staff were expected to "put up and shut up" because they loved the job.
"Lecturers tell me the education world is being destroyed - we cannot let the Government wreck our education system any longer."
History teacher Jayne Boden, from Liverpool, said parents and members of other unions had been very supportive.
"I think parents realise that the Government hasn't kept its promise to review pay scales and we have been forced into this situation."
Dennis Gibbons, an officer for the Leeds branch of the NUT, said: "There is a recruitment crisis looming in the teaching profession.
"The Government's own figures tell us that upwards of 50 per cent of trained teachers leave the profession within five years of starting due to pay, work load and pupil behaviour."
Phillippa Arnell, an English teacher at Park Community School in Havant, Hants, said "decent" rates of pay were necessary to secure the quality of people entering the profession.
"I did feel guilty when I explained to my pupils about going on strike but we just want to be treated fairly.
"Decent teachers are going to leave the profession if we do not get enough money to provide a decent standard of living."
Mr Balls visited Wentworth Primary School in Dartford, Kent, with Schools Minister Jim Knight. The two men spoke to children in the playground and then sat in on a year three maths lesson where they helped pupils with their sums.
Speaking afterwards, Mr Balls said he thought most teachers would be just as annoyed about today's strike as he was.
"I think parents across the country will be annoyed and disappointed to see schools being closed today, and I feel many teachers will feel the same way too.
"The idea that lessons are being lost is very frustrating, and I'm sure I share that opinion with most teachers.
"There isn't a justification for the strike. We have accepted in full the recommended independent pay review. Over the last 10 years teachers' pay has risen substantially."
"The most important thing is that I think teachers ought to be teaching classes and that's what parents want as well and the large majority of teachers aren't supporting the strike.
"It would be much better for us all to be talking and for teachers to be teaching and that's the message I'm sending to the NUT today."
The Times Educational Supplement said up to 5,000 schools were closed by the strike and a further 4,500 partially shut, affecting up to 2.9 million pupils.
But a DCSF spokesman said "more than 85 per cent of schools have remained open or open with some classes affected".
The Government has made it clear it believes the teachers' three-year pay deal of 2.45 per cent from September and rises of 2.3 per cent in subsequent years was "fair and reasonable" after ministers accepted the recommendation from a pay review body.
Speaking as he visited a nursery in the West Midlands, the Prime Minister described the strike as "regrettable and unjustifiable", adding: "The teachers' review body is an independent review body. They have made recommendations for three year pay arrangements for teachers.
"It is regrettable and unjustifiable that teachers are now striking when this independent body is making its recommendations.
"I hope people will see that there is no need for future action."
The Public and Commercial Services union said a strike by up to 100,000 civil servants caused "widespread disruption" across 10 Government departments and agencies, hitting driving tests, coastguard stations, immigration centres, jobcentres, benefit offices and pension contact centres.
Half of the UK's 19 coastguard control centres were forced to close and 4,000 driving tests were cancelled, said the union.
The Government said it estimated that only 44,000 civil servants were on strike.
PCS general secretary Mark Serwotka said: "The breadth and depth of the support for today's strike has been fantastic as some of the lowest paid in the public sector take a stand over pay cuts and pay freezes.
"Those on strike know, as do the independent experts, that it is not their wages that are fuelling inflation, but the ever rising energy, food and mortgage costs. It is disgraceful that the Government should hide behind such a discredited argument to force down the wages of hard working civil and public servants, some of whom are on the minimum wage."
The PCS's annual conference next month will decide whether to hold a national ballot for strikes, which could herald a summer of discontent in the civil service, while the NUT executive will decide in the next few weeks whether to press for more strikes.