Norwich's last council-run secondary school, which was placed into special measures, is being forced to become an academy by the government.
The Department for Education (DfE) said it had issued an Academy Order on the Hewett School to bring about "rapid and sustained improvement".
Hundreds of campaigners marched through the city earlier this month in protest at the plans.
Norfolk County Council said it expected a "full and effective consultation".
More than 1,300 people have signed a petition saying the Hewett School should remain under local authority control.
Supporters claim the plans would see the school become "an exam factory".
A recent Ofsted report found "immediate change" was needed, with the school being deemed "inadequate" in five of seven categories.
A DfE spokesman said: "Becoming an academy with the support of a strong sponsor is the quickest and most effective way to bring about rapid and sustained improvement.
"That is why we have issued the Academy Order. It gives staff and parents the chance to have their say, provides them with much-needed clarity, and helps to secure the long term future of the school."
James Joyce, chairman of the children's services committee at the council, said: "The Secretary of State rarely signs an Academy Order for a school without an application first being made by the school's governors or interim executive board.
"This has led members of the council and the public to raise concerns about the processes followed by the DfE thus far and the reasoning behind their decision.
"We want to ensure that the future of the school is considered in a fair and open way and expect full and effective consultation to take place before any final decisions are made.
"We have reserved our decision on whether to take legal action until we see what shape any consultation will take."