More than a fifth of teachers and school leaders believe public funding for the poorest pupils is being used to plug holes in school budgets, according to a poll.
The survey also suggests many schools are cutting back on areas such as staff, IT equipment and trips.
The findings come amid continuing concerns about a squeeze on school budgets in England. Ministers have insisted more money is going to schools.
The survey of 1,246 primary and secondary teachers and senior leaders, working in English state schools, found that 22 per cent said money from the pupil premium – extra funding to support the most disadvantaged youngsters – is being used to plug gaps elsewhere in their school's budget.
Just over a third (36 per cent) said this was not happening, and the rest did not know. Among the senior leaders polled, 34 per cent said pupil premium funding was being used elsewhere, with 57 per cent saying no.
Cuts to staff
Those surveyed by the National Foundation for Educational Research (NFER) were asked whether their school was cutting back on certain areas for financial reasons.
Some 63 per cent said their school was cutting back on teaching assistants, making it the most popular answer, with half saying there had been cuts to support staff, and 39 per cent saying there had been cuts to teaching staff.
In addition, 44 per cent said trips and outings had been cut back and 41 per cent said there had been cuts to IT equipment.
The survey was commissioned by the Sutton Trust ahead of its education summit in New York.
Trust founder Sir Peter Lampl said: "It is very worrying that schools are losing teachers as a result of spending cuts. The result is that they are also increasingly plugging funding gaps with the pupil premium."