West Sussex headteachers have welcomed the launch of a new inquiry into school funding.
A cross-party committee, chaired by Robert Halfon, Conservative MP for Harlow, will look into whether a longer-term plan for investment in education is needed.
They will also examine the effectiveness of areas such as the pupil premium - money given to schools to raise the attainment levels of disadvantaged pupils - and how the new National Funding Formula will be implemented.
The education select committee has contacted the WorthLess? campaign, which has been championing the call for better funding for three years, and invited it "to play a full and active role" in the investigation.
Jules White, head of Tanbridge House School, and one of the driving forces behind WorthLess?, said: "Parents, West Sussex County Council and headteachers have been clear that the new National Funding Formula does not, in any way, adequately address our children’s school funding needs.
"It now appears that a cross-party group of senior MPs are very worried too."
He added: ""At some point the government has to acknowledge that schools, especially in areas such as West Sussex, are being sold short.”
Launching the inquiry, Mr Halfon said: "Young people are in compulsory education for around 13 years, yet Government only plans investment in education every three or four years.
"We need to move to a situation where education funding is not driven primarily by Treasury processes but rather by a long-term strategic assessment of our national priorities for education and skills.
"Rising cost pressures faced by schools, sixth form and further education colleges have led to serious challenges in the provision of high quality education which can be a key driver for social justice and productivity."
He added: "Education provides a vital ladder of opportunity for our young people. This inquiry will examine whether it is time to have a ten-year plan for our schools and colleges, and what resources are required to put this plan into action."
On Wednesday (April 18), West Sussex MPs met with education secretary Damian Hinds to discuss issues such as the new funding formula, high needs funding and standards in schools.
Tim Loughton (East Worthing and Shoreham) said: "We made the case to the new Secretary of State very clearly. West Sussex has been at the bottom of the funding pile for too many years and we are absolutely seeing the effects of that in our schools and have done over the last year."
The National Funding Formula saw £1.3bn added to the education budget over two years, taking it to £43.5bn by 2019/20.
Describing the £28m allocated to West Sussex as "really good", Mr Loughton added: "But still the funding formula leaves too great a gap between what our schools get in West Sussex and what many schools get in Metropolitan areas, particularly London.
"We've asked him to look again at how that formula can further be improved to make sure there is not such a gap."
What the headteachers said:
Michael Ferry, St Wilfrid's School, Crawley: "Just over a year ago, the executive director of the Education Policy Institute told the education select committee that the 'government did not have a clear understanding of just how much it costs to run a school'.
"Since then we have seen this lack of a clear understanding reinforced through the proposed National Funding Formula in a way which sees the historic funding inequalities of the past simply reinforced and as such we remain in a desperate position.
"I very much welcome the inquiry and the fact that MPs from across the parties seem to be realising that the National Funding Formula doesn’t deliver what we need ie adequate funding for all schools to be able to provide a broad and balanced curriculum to meet the needs of its students.
"A renewed focus on this through the inquiry can only serve to help the argument for fairer funding."
Pan Panayiotou, Worthing High: "A cross-party Inquiry will only reveal what we as senior leaders have been saying for some time and that the funding formula is not fair by any definition and is underfunded.
"The Worth Less? campaign has been able to provide a strong platform and voice for us as headteachers and something needs to be actioned asap by Government to address the shortfall in school budgets.
"Schools are having to make difficult decisions in order to balance their budgets and sadly this is leading to a narrowing of curriculum choices and redundancies in some schools."
Mark Anstiss, Felpham Community College: "The inquiry is welcomed but will only be valuable if the government is prepared to act upon its inevitable conclusions.
"Schools in West Sussex are in a critical position: there are insufficient teachers and if they can be found then there are insufficient funds to employ them.
"Educational provision is being cut as there are simply no more efficiency savings to be made. The curriculum offer for students is being diminished and support for the most vulnerable and those with SEND are being withdrawn.
"The National Funding Formula was long over due and eagerly awaited but it has failed to deliver for West Sussex schools. There are still massive disparities in funding across the country and it is simply unacceptable that our students are worth less.
"Our country is facing significant economic challenges and the current education budget is insufficient to meet the needs of future generations."
Peter Woodman, The Weald School and Sixth Form College: "I am sure most school leaders will welcome the decision as long as it is run fairly and not along party lines. The issue of long-term investment in education is too important to get run. We need funding that is both fair and sufficient. At present it is neither."