As many as 2,000 schools will still be underfunded in seven years’ time, despite the government's school funding reforms, MPs have been warned.

Concerns about the implementation of the government’s flagship national funding formula (NFF) were raised at a Commons Education Select Committee hearing on school funding today.

The MPs also heard criticism of the money for "little extras" announced by the chancellor in last week's Budget.

Here are five key points from the evidence of education unions and headteachers:

1. Schools will be underfunded for years to come

Kevin Courtney, joint general secretary of the NEU education union, raised concerns about rules that limit the annual funding increases that schools can receive under the NFF.

The system limits the yearly cash increase that an individual school can receive to 3 per cent, meaning that some schools that are due a big increase will not receive the full amount for many years.

He said: “By 2025 there will still be 2,000 schools that haven’t reached their national funding formula level, so it’s far too slow, and that’s because there isn’t enough money in there.”

His concerns were echoed by Valentine Mulholland, of the NAHT headteachers’ union.

She said her organisation welcomes a national funding formula, but added: “The issue is that at a time of funding shortage, we can’t get people to where they should be quick enough.”

2. Minimum funding for schools ‘not enough’

Ms Mulholland told MPs that the minimum per-pupil funding for primary schools is currently set at £3,500.

Ms Mulholland said: “What we see is schools that are only receiving that minimum funding are not sustainable, absolutely not sustainable.”

She said the minimum funding level for schools was the one area of the NFF that needed looking at again, adding that anything below £4,000 is “really, really not viable”.

Julia Harnden, of the Association of School and College Leaders (ASCL), said its research concluded that secondary schools need £5,800 per pupil, compared with the current £4,800 minimum guarantee from the government.

3. Schools need ‘up to £6 billion’ extra a year

Darren Northcott, of the NASUWT, said overall education funding should be 6 per cent of GDP.

Stephen Tierney, of the Headteachers’ Roundtable, called for a £4 billion annual increase in the schools budget.

Ms Harnden said it was not possible to give a figure because there was currently no agreement about what is expected of the education system.

Jules White, headteacher at Tanbridge House School in West Sussex, and founder of the WorthLess? School funding campaign, called for a 15 per cent increase in the school budget, which he said amounted to £6 billion more a year.

He said this was made up of £2.7 billion “to reverse the real-terms cuts”, £1.5 billion to £2 billion to support high-needs funding, and £1.3 billion to “prime the national funding formula properly so we can begin to close the gaps between the very lowest and the best-funded areas and address some of the real-terms costs”.

4. Pupil premium ‘propping up core school budgets’

Pressures on schools' budgets mean many are using the pupil premium, which is designed to target support at disadvantaged children, to plug holes in their core budget, MPs heard.

Mr White said: “We did a survey of 1,700 heads up and down the country and 90 per cent said they were spending at least a proportion of pupil premium funding on propping up their core budgets, and about 50 per cent said they were spending over half.

“I’m certainly doing that in my school. Apparently, I’m breaking the law doing that but I have got to make ends meet.”

Mr Courtney said that “schools are in practice sometimes [moving] money from the pupil premium because they do not have enough money in the rest of their budget, and I would not like to get involved in talking down those schools”.

The witnesses had mixed views about whether pupil premium funding should be ring-fenced.

Mr White said it should not be, while Mr Northcott said it should, “because then you make sure it is spent on the purposes for which it is intended”.

Ms Mulholland added that “it would be really difficult to ring-fence pupil premium”.

5. Lack of clarity about what society expects of schools

Ms Harnden told MPs that clarity about what is expected of schools is needed before their funding levels are discussed.

She said: “We need a very clear understanding of what the national ambition for education is, because if we are in schools and colleges being asked to broaden our remit, and the breadth of expectation is broadening quite significantly, we need to be very clear on what that actually is, and then we can start to think about what are the appropriate levels of investment that will meet the cost of those services.

“There is no doubt that cuts or shrinking of other services around schools are impacting significantly.”

Her view was echoed by Mr White, who asked: “Why are we responsible for all of society’s other ills?”

Witnesses supported calls from committee chair Robert Halfon for education to have a 10-year funding plan, similar to the NHS.