According to the figures from a joint survey by the NAHT and The TES, in which nearly 1,500 headteachers and school business managers took part, this year's schools' settlement will lead to 40 per cent of schools seeing their budgets drop.
The numbers show that 35 per cent of schools will see a decrease in funding of up to 10 per cent, while a further 5 per cent - approximately 1,000 schools - will see a drop of 10 per cent or more.
But while some schools will see their budgets squeezed over the next 12 months, almost exactly the same number of schools are seeing their funding increase.
Overall, the coffers of 35 per cent of schools will swell by up to 10 per cent over the coming year, and a further 4 per cent of schools will see a rise of more than 10 per cent.
Just a fifth of schools will see no change at all to the funding they receive. Among the most striking findings is that some 17,000 jobs face the axe, with just 5,000 created by other schools. This will leave a net reduction of 12,000 jobs.