Today more than 70 headteachers and education leaders from all corners of Cumbria are pleading with the Chancellor to take action on cuts to school funding.

They say they are finding the current situation "untenable" - with fears that children will suffer.

Scores of headteachers, senior school leaders, bursars and governors have signed a letter urging Philip Hammond to take action as he prepares to deliver his Autumn Budget in November.

One of their greatest fears is that the county's vulnerable children will suffer the most as schools seek to shed staff to balance the books.

In their two-page letter, they call on him to ensure that future funding allows them to maintain quality provision.

They have also set out a catalogue of concerns which includes:

* cuts to other local services resulting in schools picking up the cost;

* rising payroll costs including increased pension contributions;

* lack of investment and over-due repairs for buildings "presenting health and safety concerns";

* equipment and resources not being replaced;

* staff redundancies leading to cuts in support for those with special needs or disabilities;

* a reduction in the number of subjects schools have the capacity to teach.

Cumbrian school leaders also say that current shortfalls in funding are "causing tensions" between the county's cash-strapped large secondary and primary schools and the small, rural schools which are the "life-blood" of many communities.

The school leaders' letter states: "In Cumbria we are very proud of the high reputation we have for inclusive practice, with the vast majority of special educational needs and disabilities being met within mainstream school settings, unlike many other parts of the country in which these needs are met by a concentration of expertise within a greater number of special schools.

"Being “Inclusive Cumbria” means that the expertise to meet these needs is spread across the school system, and predominantly consists of highly trained and skilled teaching assistants.

"Between 80 per cent and 90 per cent of a schools’ budget is staffing costs, and Cumbrian schools are reporting that in order to set a balanced budget they are already having to make staff reductions or plan for them within the next few years.

"We fear that some of our most vulnerable pupils will be hardest hit by the funding pressures our schools are being forced to tackle."

Campaigners say that latest figures show Cumbria's schools will face a shortfall of £13.3m by 2020, the equivalent to a loss of £226 per pupil or the salaries of 272 teachers.

The figure was £23m before the impact of a new National Funding Formula and other changes announced by the Education Secretary Justine Greening last month was evaluated.

The letter adds: "While we commend the intention to redistribute funding more fairly through the National Funding Formula, we believe it will only succeed if there is sufficient funding within the overall schools budget."

The headteachers and school leaders also insist that a "one-size-fits-all calculation" for the future viability of schools will not work for Cumbria.

"The wider implications of our geography need to be factored in to any future calculations of school funding distribution at a national level," their letter states.

The letter is the latest push from members of the Cumbria branch of the National Association of Head Teachers.

The branch has been campaigning and lobbying MPs and ministers on the school cuts issue.

Its leaders were also involved in staging demonstrations in Penrith and Carlisle, which saw hundreds of parents, children and supporters turn out.

A series of public meetings have also been held and and the northern TUC network of unions held an education forum in Carlisle last month.

The branch is keen to work with all six of Cumbria's MPs and has sent a copy of the letter to each one - from Carlisle's John Stevenson to Copeland's Trudy Harrison, who sits on the Education Select Committee, and Barrow's John Woodcock.

Cumbria NAHT branch secretary Graham Frost, headteacher of Robert Ferguson Primary School, Denton Holme, Carlisle, said: "All across the country, people from all walks of life, who recognise the value of a good education, are waking up to the stark reality schools are squaring up to.

"We simply must invest in education now - our children are depending on us to get this right.

"We hope that the Chancellor of the Exchequer will take our letter very seriously and consider it his ambition and moral duty to fund schools fully and fairly, taking all the costs into consideration."

He added: "By providing a clear overview of the particular challenges the current level of underfunding presents to Cumbria’s schools, we also want to help our politicians to champion the cause of Cumbria’s children in Westminster."

The letter was sent to the Chancellor over the weekend.

Sue Blair, headteacher at Pennine Way Primary School in Harraby, Carlisle, is among the signatories.

She said: "Schools are facing three per cent reductions by 2021 at a time when the expectations are growing in terms of what primary schools must provide to ensure pupils are educated and safeguarded.

"In order to meet the ever expanding needs of our pupils we are being asked to make decisions that leave governing boards, staff and parents extremely frustrated and very saddened. Leaders are being compromised.

"Schools are, as ever, being amazingly creative in trying to seek alternative solutions to the funding crisis, but there comes a point when we can do no more."

She added: "At a time when recruitment in teaching is at an all-time low and at a time when mental health issues are at an all-time high, we seem to be entering into a no-win situation and my concern is that it is our children who will end up as the losers.

"The stark reality is that schools need more funding if we are to continue to provide the excellent service we strive to deliver for our children, families and communities."

Fellow signatory Rebecca Stacey, headteacher at Castle Carrock School, said: "The biggest issue is that schools face confusion and uncertainty with continuously increasing costs."

Last month Education Secretary Justine Greening pledged that schools in England will get more money per pupil under "historic" reforms of the funding system.

Under the biggest overhaul for decades, a new "national funding formula" (NFF) is to be introduced, which will see money distributed according to the individual needs of each school.

Minimum funding levels are to be set at £3,500 per primary school pupil in 2019/20 and £4,800 per pupil in secondaries.

The NFF is an attempt to allocate money to schools in a fairer way. Each school will get a basic amount of funding per pupil, and then additional funds based on factors such as deprivation, rurality and low prior achievement of pupils.

Ms Greening also announced in the summer that an extra £1.3 billion would be found for schools from existing budgets, but some unions argue that this will not be enough to plug growing funding gaps.

The Government says spending on education is at record levels and with additional funding pledged it will almost £41 billion in 2017/18, £42.4 billion in 2018/19 and £43.5 billion in 2019/20.