Converting all schools to academy status will cost council taxpayers £320 million, the Local Government Association (LGA) has warned.
The move would also see local authorities lose £80 million a year in business rates income, according to the LGA.
The LGA, which represents councils across England, insisted converting all schools into academies would have a negative impact on educational standards as it called on the Government to spell out its controversial plans in greater detail.
A survey of LGA members found that the cost of the change-over would reduce to £120 million if the schools were allowed to operate as stand-alone organisations, rather than be sponsored.
This is because under the sponsored model any debt built up by the school generally remains with the council, the LGA said, as it also warned of the high legal costs involved in changing to academy status.
Chairman of the LGA’s children and young people board, Councillor Richard Watts, said forcing schools to become academies would be bad for pupils.
“If all schools are encouraged to become academies at some point, this will have significant financial implications for councils.
“We have remained strong in our opposition to all forced academisation, and this opposition has been echoed by MPs, teachers and parents. Recent evidence from Ofsted has also proved that forcing a school to become an academy doesn’t in itself lead to better exam results.
“The Government has also offered academy chains £600 million to help them convert more maintained schools. But councils have seen that same amount cut from the Education Services Grant.
“This crucial grant would have been used to help protect children and ensure that they do their very best in school. It would also have paid for background checks for staff, speech and occupational therapies, physiotherapy and tackling truancy.
“The money that councils are predicted to lose could be better spent on recruiting, training and keeping excellent teachers, and making sure children are safe and have the equipment and support they need, in buildings that are fit for purpose.
“Our recent analysis of the grades achieved by all schools under the more rigorous Ofsted inspection framework proved that 81% of council-maintained schools are rated as ‘good’ or ‘outstanding’, compared to 73% of academies, and 79% of free schools.
“These schools should not be forced down the academy route unless they make that decision themselves.
“Councils should be seen as education improvement partners. We want to work with government to ensure every child gets the very best from their years at school,” Mr Watts said.