Oldfield School in Bath is the city's first academy
The first secondary school to become an academy in Bath has now officially left local authority control.
The council approved the move after Oldfield School, currently an all-girls school, changed its plans for a single-sex academy to a co-educational one.
Conservative-run Bath and North East Somerset council had threatened to shut the school if it did not agree.
The school will no longer report to the council but instead will report to the Department for Education.
The council has said it will provide £1.85m and manage the necessary work to ensure boys can be admitted in year seven from September 2012.