Buckinghamshire is to lose nearly 450 teachers by 2020, according to the National Union of Teachers (NUT).
They say the severe cuts in school funds will see the county's schools receiving £16 million less in three years.
Overall, the NUT suggests schools will lose an average of £339 per primary pupil and £477 per secondary pupil because school funding is frozen.
NUT Divisional Secretary Annette Pryce said this will be detrimental to Buckinghamshire schools.
She said: “Under this Government’s funding policies, there are no winners, only losers.
“Buckinghamshire schools are being forced to make decisions that no head teacher should have to make including reducing school staff and teachers, increasing class sizes, and reducing the range of subjects offered simply to balance the books.
“This is an unacceptable state of affairs - the NUT and ATL will continue campaigning for additional funding, to protect schools and our children’s education.”
The NUT's School Cuts website suggests that some schools in the county could lose over £200,000 by 2019.
One example is Amersham School, which School Cuts say will lose £226,625 and six members of teaching staff.
Another is Chiltern Hills Academy, in Chesham, which apparently will lose £418 per pupil and seven teachers by 2019.
However, a statement made by Zahir Mohammed, Cabinet Member for Education and Skills at Bucks County Council, contradicts NUT's negative forecast.
He said: “We have worked hard to improve the funding of our schools and I have said publicly many times that seven out of the ten lowest funded schools in the country are here in Buckinghamshire.
“But, far from a reduction in funding, Buckinghamshire received an additional £18 million a year for the past two years and - if the current consultation is implemented - will receive another £10 million a year to help the lowest funded schools.”
The Cabinet Member said 54% of national schools will gain from the budget changes and 46% will lose, but overall 85% of Buckinghamshire schools will gain funding.
However, Annette Pryce from NUT suggested that this did not necessarily mean Bucks will benefit, as the figures take no account of inflation and the rise in pupil numbers.
She said: “It is true that Bucks schools stand to lose less per pupil than any other authority in the Region (5% between 2015/16 and 2019/2020), but this is still a significant cut.
“The Government is keen to define its new funding formula as 'fair funding', but this is nonsense - it cannot be fair without new money. There is a gaping hole in the school budget and it is only set to increase through inflation and a rise in pupil numbers.
“98.5% of schools will see their funding per pupil fall in real terms - unless the Government does the right thing and allocates more money, schools will together lose £3 billion a year in real terms by 2020.
“As it is, the Government is simply shuffling the same inadequate funds around the country.”
To find out how the NUT believes your child's school will be affected, click here.