Millions of pounds of debt has been inherited by councils across England as schools convert to academies, a BBC investigation has revealed.
Opponents say local authorities are forced to use their government education grant to clear the debts.
A BBC Freedom of Information request shows more than £30m has been cleared.
The Department for Education said local authorities should pay the debts as they were accumulated when the schools were under council control.
The Local Government Association said vital cash was being taken from schools not involved in the scheme.
The BBC’s FOI to all local authorities in England revealed £32.5m has been spent by councils on clearing debts since the Academies Act was introduced in 2010.
Under the academies scheme, when council-maintained schools choose to convert, local authorities have to pick up the tab for the costs of conversion including the cost of any deficit and legal fees.
David Simmonds, deputy chairman of the Local Government Association, said: “It is not fair that some schools are burdened with a deficit while other schools can walk away and leave that debt behind at the detriment of other schools in the community.
“It is not right that the taxpayer foots the bill. This money could instead be spent in ways which directly benefits pupils.”
In 2012, education chiefs in Birmingham refused to write off at least £1.3 million of debts owed by schools converting to academies. By 2013, there were fears Birmingham’s school budget could run out if the practice continued.
A Birmingham City Council spokesman said: “All of Birmingham’s children must benefit from any changes to the education system, so we need the government to make changes to enable this to happen so school and council budgets, that are already stretched, are not strained even further.”
Councillor John Jones, Blackpool Council’s cabinet member for school improvement, said local councils having to pick up the tab to write off debts was “extremely frustrating”.
Jonathan Bacon, from the Isle of Wight Council, said other schools missed out when £1.4m was paid for a school to become an academy.
Local authorities said they use the Dedicated Schools Grant to pay the school debts. The grant is paid by the government to local authorities as the main source of income for the schools budget.
A Department for Education spokesperson said: “Councils are only required to cover a school’s deficit when it has become a sponsored academy after a prolonged period of underperformance, and the deficit was accumulated under council control.
“Academies are a vital part of our plan for education and are transforming the education for millions of pupils across the country.”
Christine Blower, from the National Union of Teachers, said: “This is another example of the financial pressures that the academies policy has brought to bear on local authorities’ education budgets.
“As a direct consequence of the academies programme, local authorities have less money to fund and support other schools.”