Around half of schools in Sheffield are no longer controlled by the local authority - showing the startling growth of the academy programme in the city.
Sheffield now has 81 schools which are academies, with sponsors including other schools, businesses and churches - with another nine in the process of converting to academy status.
The final three secondary schools under Sheffield Council control applied to join the Minerva Learning Trust last year.
Academies are state funded schools which are run outside of local council influence with greater freedom over pay, conditions and what they teach.
READ MORE: Teacher who threw piece of metal at pupil in Sheffield banned over dishonesty
They control their own admissions process and have more freedom, such as changing the length of the school day and term times.
Academies are overseen by academy trusts, and increasing numbers are part of chains, otherwise known as multi-academy trusts, with some running schools across the country.
Astrea Academy Trust has 18 schools in South Yorkshire, including six in Sheffield.
Its chief executive Libby Nicholas said: "Each of our academies retains its own unique personality and characteristics, but benefits from the network of support and challenge that comes from being part of Astrea.
READ MORE: Crisis-hit academy chain cleared after police investigation
"At a practical level there are significant benefits too – our size means that we can make considerable savings on all sorts of things, from ICT and supply teachers through to pritsticks and paper.
"These savings go back into our classrooms, meaning we can spend more money on what really matters in education.”
The DfE announced last month that it was investing millions of pounds into academies in Yorkshire to improve and expand facilities.
A Department for Education spokesman said: “Thanks to our reforms and the hard work of teachers academic standards are rising, with 1.9 million more pupils in good or outstanding schools compared to 2010 – 480,000 of those pupils study in a sponsored academy that was typically previously underperforming.
“We are investing around £30 million to support multi-academy trusts across England to improve other schools.
READ MORE: WE ARE SHEFFIELD: Retiring guide dog is much more than man’s best friend
"Academies allow schools to make their own decisions based on local need and the interests of their pupils.”
The DfE added that of all the schools taken out of local authority control across the country and made into a sponsored academy, 65 per cent have seen their grade improve from inadequate to either good or outstanding.
Earlier this year the Public Accounts Committee called on the Government to do more to challenge academy trusts after it emerged they may be using taxpayers’ money to pay “unjustifiably” high salaries to senior staff,
Its report also warned that there is a lack of transparency at multi-academy trusts, which are educating increasing numbers of children and handling large amounts of public money.
It follows a shock announcement last September that Wakefield City Academies Trust would cease running 21 Yorkshire schools.