Secondary schools face losing hundreds of thousands of pounds from their budgets if planned cuts go ahead.

Cockermouth School could lose £750,000 by 2020 if a proposed new funding formula is applied in full.

And Keswick School has warned that non-essential subjects and extra-curricular activities could be put at risk as it is facing potential losses of more than £600,000.

Both schools draw pupils from a wide area in West Cumbria.

Rob Petrie, headteacher at the 1,350-pupil Cockermouth School, said: “We would lose £750,000 in total over the next few years if the proposed funding formula was applied in full.

“It was under consultation when purdah began [preventing political decisions during an election] and so there is still work to be done before we can predict the impact with any accuracy.

“The proposed formula doesn’t factor in sixth-form funding, nor the increase in student numbers joining our school.

“Whichever party is in power, it is vital that schools receive clarity about their future funding so we can budget effectively for the next few years.”

Keswick School has announced plans to cut staff and charge for some GCSEs and outdoor activities.

The school is also seeking sponsorship to maintain a number of roles and wider extra-curricular opportunities across the school, including the rugby coach, languages assistant, music groups and IT hardware.

Headteacher Simon Jackson said the school, which has more than 1,250 pupils, was being put at risk by the reduction in funding it has seen over the last four years.

The school is looking at a budget reduction of £602,777 by 2020.

In a letter to parents, he said there had been a lot of misinformation about school funding and clearly figures could be manipulated. But he said the view that there had never been more funding in education was misleading and did not reflect the proposed huge reduction in base funding to support each child in secondary school.

Mr Jackson said the reduction would particularly affect his school as it did not receive significant top-up funding for pupils for whom English is an additional language or for deprivation.

He said: “This is about our life chances for young people. It’s just crazy that the government and politicians don’t understand that investment in the future is investment in education.”

In the face of the cuts, Keswick School has decided not to renew fixed-term contracts for some extra-curricular roles unless sponsorship can be found. It also plans to charge pupils who take up GCSEs in astronomy, dance or Latin, or who want to undertake Duke of Edinburgh awards.

Dr Petrie is calling for an increase in funding.

"There needs to be an increase in the funding per student that schools receive to balance the increasing pressures due to inflation and employer contributions; this is the only solution that fully safeguards high quality teaching and learning," he said.

"We have already taken significant action to reduce costs and improve efficiency without impacting on the student experience.

"These savings will be realised in the next few years and, alongside continued tight cost control, will enable us to continue to offer the full range of learning opportunities to our students."