Leicestershire schools are among the lowest funded in England – and yet almost half of them will lose under the new formula.
Worst-hit is Rendell School in Loughborough, serving an area which is among the poorest 30% in England.
Almost two-thirds of pupils are from minority ethnic backgrounds.
It is a successful school, rated good by Ofsted, which aims high academically, promotes sport and keeps class sizes small
But from September next year, the school is due to lose almost the maximum amount possible under the Fairer Funding Formula.
The maximum cut under fairer funding is capped at 3% and, according to head teacher Karen Rixon, Rendell is due to lose 2.8% – the joint highest in the county, despite by no means being the best funded.
This amounts to about £34,000, equivalent to at least one teacher’s salary, Mrs Rixon told BBC News.
She describes the cut as “pretty shocking”, particularly as, she says, schools in other more affluent areas of Leicestershire, will see their budgets rise by up to 8%.
“The biggest thing for me is the reality that schools that are funded by huge amounts more than us are not going to be losing out,” said Mrs Rixon.
“There is not going to be a redress of balance.”
The school is already under major pressure, as funding has failed to keep pace with increased staff costs, such as increased pension contributions and pay rises, said Mrs Rixon.
She said the school was looking at ways to cope with the loss in funding.
“If we lose a teacher it will push class sizes over 30,” she explained.
“Whereas some schools can raise significant amounts of money to enrich facilities in schools, Rendell is very much reliant on government funding for everything it provides, including enrichment activities.
“It is these things we will have to cut back on first to protect the jobs of teachers and support-staff,” she added.
So far, the school has not had to dip into its reserves, but this could happen over the next few years, she warned.
“I have managed the budget well but there is very little room for manoeuvre in any way.”