Image copyright Getty Images Image caption The spending watchdog says schools will have to find £3bn in budget cuts

A head teacher has resigned in protest over the school funding crisis, telling parents she had not gone into teaching to cut the number of teachers or increase class sizes.

Mary Sandell, head of the Forest School in Winnersh, Berkshire, has written to parents about "bleak" funding problems.

Head teachers across England have been warning of budget shortages - with threats of cutting school hours.

The Department for Education has said schools have record levels of funding.

In a letter sent to parents, the secondary school head teacher warned of the worsening impact of a lack of funds.

"I feel unable to deliver the quality of education the boys at The Forest so clearly deserve," said Ms Sandell in her letter, informing parents of her "deep regret" about her decision to resign.

"The situation with regard to schools funding, both nationally and locally, is bleak.

"In common with other head teachers, I did not enter the teaching profession to make cuts that narrow the curriculum, or to reduce the number of teachers and increase class sizes, and yet my hand has been forced, and I see no immediate easing of the situation.

"In addition, there is an acute teacher shortage, which is really beginning to bite."

Strike threat

School leaders across England have been complaining about a funding shortage - with the National Audit Office warning that schools face budget cuts of £3bn.

As well as concerns about overall school funding, there have been worries that a new formula for allocating cash has left schools in some areas without adequate budgets.

A number of Conservative backbenchers have called for a rethink on the funding plans.

Head teachers in Cheshire have said a lack of cash might force them to cut school hours and school governors in West Sussex have threatened to go on strike for the first time, rather than sign off underfunded budgets.

Ministers have revealed in an answer to a Parliamentary question that more than half of academies lacked enough income to cover their expenditure.

Heads have been calling for the return of £384m announced for turning schools into academies, which it was revealed had been taken back by the Treasury.

The Department for Education has defended funding levels, saying that more than ever is being put into schools - and that the new funding formula will tackle longstanding unfairness.

"The government has protected the core schools budget in real terms since 2010, with school funding at its highest level on record at more than £40bn in 2016-17," said a Department for Education spokeswoman.

"But the system for distributing that funding across the country is unfair, opaque and outdated.

"We are going to end the historic post code lottery in school funding and under the proposed national schools funding formula, more than half of England's schools will receive a cash boost.

"In Wokingham funding would go up by 2.1%, over £1.7m, if the proposed new funding formula was implemented."