MORE than 500 head teachers have written the Prime Minister an open letter demanding that she scrap plans for £3billion worth of cuts to education.

School leaders say they are concerned that standards will fall if the government is unwilling to give more money to education.  Staff are reportedly having to ask parents for money, and are cutting back on subjects.

Ministers have previously said that school funding is at record levels, and this will increase further over the next two years as pupil numbers rise.

But the National Association of Head Teachers general secretary Russell Hobby accused the current government of "flatly refusing to admit the reality" of the pressures schools are facing.

Speaking as the union met for its annual conference in Telford, Mr Hobby said: "Ministers should no longer be allowed to claim that school funding is protected.

"To make ends meet school leaders will be forced to make staff redundant, cut subjects, increase class size and cut back on extra-curricular activity.

"On the steps of Downing Street the Prime Minister promised a country that works for everyone. That begins with our children.

"If we're serious about that as a nation, we need to be prepared to pay for it. June 8 is a tipping point.

"What worries school leaders is that if we have a government that is unwilling to fund education fully and fairly we'll see a domino effect where progress stalls and standards fall in every school."

The union said its own research had shown that two thirds of school leaders (66 per cent) say they are cutting hours for teaching assistants, while just under a third (31 per cent) are reducing staff hours.

Mr Hobby added: "All schools are operating under unacceptable levels of financial pressure.

"This is a result of the government's choice to freeze spending and keep it at 2010 levels for each pupil.

"You can't expect it to. But the government is flatly refusing to admit the reality. Until they do, all schools are at risk."

The average secondary in England is facing losses of almost £300,000, while primaries will lose out on tens of thousands of pounds, according to the Education Policy Institute (EPI) study.