Schools in Norfolk and Cambridgeshire are among those facing millions in lost funding because of a miscalculation by the government.
The Department for Education had initially said it would be increasing the amount of school funding per pupil by 2.7 per cent in 2024/25.
However, due to the error this increase is now going to be 1.9 per cent per pupil.
Norfolk County Council said the new figures mean £5.6 million less for the county and that all mainstream schools will not receive the level of funding they were expecting.
Councillor Penny Carpenter, Norfolk County Council’s cabinet member for children’s services, said she had written to the Department for Education to express her frustration.
She added: “I sympathise with schools placed in this unfortunate position by the Government’s error in July.
"We will work with schools and academy trusts to help them fully understand the details of the announcement and its impact."
