Almost 7,000 schools may be closed for the day as teachers stage a walk-out over pay.
A survey of half the local authorities suggest that 28 per cent of schools are expected to be disrupted on Thursday as a result of the NUT strike.
Education Secretary Ed Balls said that he genuinely did not believe that teachers wanted to strike.
The 88 local authorities surveyed, half of the total, collectively believe that 3,400 schools will be disrupted.
If the pattern is true of the rest of local authorities across the country, it would mean that 6,800 schools will close for the day or have lesson disrupted.
The NUT argues that teacher's pay should rise in step with the level of inflation – 4.1per cent.
They are protesting about a 2.45 per cent rise this year with a further rise of 2.3 per cent in 2009 and 2010.
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