According to the research, announced by ATL, GMB, NAHT, NUT, Unison and Unite, every parliamentary constituency in England faces a loss in funding per pupil by 2019.
The government published detailed proposals for its funding formula on 14 December and a consultation is running until March.
The biggest loss forecast is for Bermondsey and Old Southwark in London, where per pupil funding is predicted to fall by £1,051.
Funding is also set to fall by £377 in Maidenhead, prime minister Theresa May’s constituency, and by £655 in Putney, where education secretary Justine Greening is the MP, according to the research.
An average loss of £339 per primary pupil and £477 per secondary pupil is predicted. Details of forecasts for individual schools are published on schoolscuts.org.uk.
The figures assume that inflation for schools will amount to 8.7% over the lifetime of this parliament, as estimated by the National Audit Office in its Financial sustainability of schools report, published in December.
Mary Bousted, ATL general secretary, said: “It is incredibly difficult to produce a formula that funds all schools in England fairly, but unless the government puts more money into the overall budget all schools will struggle to make ends meet.”
Separately, research from the Association of School and College Leaders, also published today, said per pupil funding would fall in some of the areas that are currently the lowest funded.
The union forecast that per pupil funding would fall by 2.1% in Cheshire East and by 0.4% in Trafford. Both areas are currently in the lowest 10 funded areas in England.
ASCL interim general secretary Malcolm Trobe said: “The government is trying to slice up a cake which is too small. It needs to put more money into the system and make education a political priority.”
Commenting on the figures put out by the six teaching unions, a DfE spokesman said they were "fundamentally misleading". Under the proposed national schools funding formula, more than half of England’s schools would receive a cash boost in 2018-19, he said.
"What the unions are doing is blurring two separate debates – the total level of funding for schools and the distribution of that funding," the spokesman said.
"They have completely ignored the fact that as pupil numbers rise so will the amount of money schools receive."
“However, we recognise that schools are facing cost pressures, which is why we will continue to provide advice and support to help them use their funding in cost effective ways, including improving the way they buy goods and services, so they get the best possible value for their pupils.”
