Hundreds of schools will be forced to close this month when teachers hold their first national strike in 21 years, in a protest over pay.

The strike, announced by the National Union of Teachers yesterday, is the first real challenge to Ed Balls, the Schools Secretary and Gordon Brown’s closest ally. Ministers responded by accusing members of the NUT, largest teaching union, of jeopardising children’s education.

The union is demanding a 4.2 per cent salary rise to match inflation, saying that the current deal is in effect a pay cut. It wants almost double the 2.45 per cent that teachers will receive this year as part of a three-year deal, with 2.3 per cent in 2009 and 2010.

The strike, scheduled for April 24, would be the first since the mid1980s, when repeated industrial action wreaked havoc on lessons. It is timed to take place a week before local government elections and will hit thousands of schools in England and Wales in the build-up to exams.

Sources at the union said it would talk to the Government until the last minute, potentially allowing an eleventh-hour resolution. But officials at the Department for Children, Schools and Families (DCSF) said that there would be no concessions or compromise.

More than three quarters of those who voted were in favour of the strike but, at 32 per cent, the turnout was considerably lower than that for other recent strike votes in the public sector.

Last night there seemed little indication that the NUT was willing to escalate its action if its demands were not met. Steve Sinnott, the union’s general secretary, said: “We’re not planning further action at this stage, just one day of action.”

Mr Sinnott denied that the strike would alienate parents, saying: “Many of them remember the days of teacher shortages and retention problems, which coincided with below-inflation salaries.”

Other teaching unions are unlikely to join the strike.

John Dunford, the general secretary of the Association of School and College Lecturers, said: “I am disappointed that the NUT has voted in favour of strike action over a pay award that represents a good deal for teachers in the present climate.”

Chris Keates, the general secretary of the NASUWT, said: “The majority of members recognise that, compared with other public sector workers, they have fared relatively well.”

Mick Brookes, the general secretary of the National Association of Head Teachers, said he did not think that a strike would persuade the Government to increase its offer.

Teachers’ pay has increased significantly under Labour. A newly qualified teacher in 1997 started on £14,000. Today, the figure is closer to £21,000. A teacher at the top of the classroom pay scale in 1997 received £21,318 but would now be on £34,281.

Times Recommends

• 5 Christmas romance confessions
• Has champagne lost its sparkle?
• Your tailor-made Christmas