Schools in England are being promised an extra £1.3bn per year in their budgets, alongside a shake-up of how funding is allocated.
But the cash for schools will be taken from elsewhere in the education budget, such as building free schools.
Education Secretary Justine Greening said she recognised there had been public concern over school funding during the general election.
But Labour’s Angela Rayner said there “wasn’t a penny of new money”.
“They are not committing any new money and have not been clear about exactly what programmes they will be cutting to plug the funding back hole,” said Ms Rayner.
“The government finally appears to be listening,” said Jules White, a West Sussex head teacher who co-ordinated a campaign over funding shortages.
But he cautioned that any increase would need to keep up with “rising pupil numbers and inflationary costs”.
Geoff Barton, leader of the ASCL head teachers’ union, said this was a “step in the right direction and an acknowledgment of the huge level of concern around the country on this issue”.
But he said schools would still have to see the implications of the money being “saved from elsewhere in education budget”.
Chris Keates leader of the NASUWT teachers’ union called Ms Greening’s statement “a recycled announcement of recycled money”.
School funding became a major issue during the general election, with school leaders and teachers’ unions warning that budget shortages would mean cuts to staffing and subjects.
They pointed to evidence from the National Audit Office and the Institute for Fiscal Studies, which warned of £3bn funding gap and schools facing an 8% real-terms budget cut.
During the election, the Conservatives had promised an extra £1bn per year, which on top of planned increases, would mean the school budget rising by about £4bn in 2021-22.
The Institute for Fiscal Studies had said that this represented a 2% to 3% real-term cuts in per pupil spending, because of rising costs and pupil numbers.
Under the plans announced by Ms Greening on Monday, the overall core schools budget will rise from £41bn in 2017-18 to £43.5bn in 2019-20.
As well as concerns about the overall amount of money available, there has been controversy over how it is divided between individual schools.
Ms Greening said the new formula would go ahead and would address unfair and inconsistent levels of funding.
Under the new arrangements, from 2018-19, the minimum funding per secondary pupil would be set at £4,800 per year.
For many years there have been complaints that schools in different parts of the country were receiving different levels of per pupil funding.
Details of an updated version of the formula, with budgets for individual schools, are being promised for the autumn.