Redundancies are being made at Banbury Academy as the trust running the school and three others in town fights deficits of around £250,000.
Academy bosses will not say how many jobs will go but have confirmed they will affect support staff.
They say they do not anticipate teacher workload increasing.
“Banbury Academy needs to restructure support staff in line with the reduced size of the student population,” said spokesman John Moss.
“Schools are funded by the government based on pupil numbers and since the school population has dropped by around 100 pupils in each of the past 10 years the staffing needs and funding have correspondingly decreased.
“The good news is that from 2016/17 the student population is scheduled to grow as there are more pupils in the local primary schools.”
Figures in last year’s accounts for the Aspirations Academies Trust (AAT) puts Banbury Academy’s shortfall at £47,547, the Space Studio’s at £117,676 and Harriers primary academy’s at £91,376. Only Dashwood primary academy was not in deficit.
The schools have been charged £323,159 for AAT services, including staff training and development, access to AAT’s intellectual property, financial services, HR and management services.
AAT directors, married couple Steve and Paula Kennings hit the headlines in the national press last year for receiving salaries of £225,000-£230,000 and £176,000 respectively.
They also receive income as the two founder-directors of Aspire, a teachers’ recruitment company set up two years ago, which charges their academies for supply of staff.
Banbury Academy is to realise substantial funds from the sale of a large sports field. However that windfall - the size of which is not yet known as the trust is negotiating with several housing developers - must go to pay for facilities for students.
Mr Moss said: “A condition of the sale of the land is that the income has to be spent on new sports facilities for the school and local community. The only amounts to be used otherwise are to cover costs incurred in relation to the sale.”
Mr Moss said the reduction in staff numbers will be managed largely through natural turnover of staff with minimal redundancies.
“There is always a turnover of staff in schools, as there was last year, which we would not describe as an exodus,” he said.
“The current process is subject to a consultation with the staff affected, so it would be inappropriate at this time to talk about numbers and roles involved as that may well change as the process goes on. Any functions carried out by staff who are leaving will either be dropped or will pass to other staff. However we do not anticipate adding to teachers’ workload.”