Almost half of private schools are cutting spending and many are raising fees as the economic downturn continues, a poll suggests.
The survey of private school teachers also suggests many face pay freezes.
Nearly half (46.1%) of the 1,483 staff questioned by the Association of Teachers and Lecturers expected reduced spending in their schools this year.
Just under one in four (23.2%) were not expecting cuts, while almost a third (30.7%) did not know.
At the same time, more than a quarter of teachers questioned said their schools had increased fees by 2% or more, with one in 10 (9.8%) saying they had risen by more than 4%.
Almost two-thirds (62.5%) said they were not expecting their school to make redundancies this year. But more than a third (35.9%) said they did not get a cost of living pay rise in 2011.
A further 18.9% said they had been given a rise of no more than 1%. One Hertfordshire teacher told researchers: "I do not expect a pay rise for the next two or three years."
The survey also reveals differences in the fortunes of private schools. While some are expanding, others are seeing their pupil numbers drop.
About a third (37.4%) of teachers said their school now has more pupils compared with the same point last year, while more than one in four (27.6%) said they had fewer students.
About a third (30.7%) said their pupil numbers had stayed the same.
A teacher at a Lancashire boarding school said: "We certainly seem to be recruiting fewer pupils from within the UK and Europe, but more from Nigeria."
Another teacher said the economic downturn had made parents less willing to pay private school fees, saying they had seen "fewer acceptances due to competition from good local grammar schools and parents less willing to commit to £10,000-plus a year in the current climate".
ATL general secretary Dr Mary Bousted said: "The majority of staff in independent schools are feeling the full pain of a pay freeze or a well-below inflation increase.
"But despite this, many are being expected to work longer hours and take on more duties. While it is understandable that schools need to keep their costs down in the current economic climate, it is not acceptable for any to use it as an excuse to exploit their staff."
A spokesman for the Independent Schools Council said at a time of economic turbulence most businesses looked hard at their costs.
"As for fee increases - if one compares the rates quoted below to the prevailing CPI/RPI figures, these are below-inflation increases.
"And ATL's own stats show that two-thirds of teachers questioned reported the same or greater numbers of pupils in their schools this year compared to last.
"To be clear - no-one in the sector is complacent, and schools of course value immensely their excellent teaching workforce - one of the main reasons that parents choose independent schools."