The decision to close a Bath boys' school has been backed by a council scrutiny committee.
Councillors decided in November that Culverhay School would stop taking new pupils into year 7 in September 2012 and then eventually close.
The closure was backed despite a public consultation showing 74% were against the school closing.
Campaigners now say they will now start a legal bid to try to keep the school open.
Deputy headmaster Sean Turner said they were considering their options.
"We are prepared to go down any road to get the right resolution to this," he said.
The boys' school, which is about half full, had considered introducing girls in a bid to remain open.
Alternatives included a co-educational academy in partnership with Bath Spa University or reducing admission numbers at other schools to boost Culverhay.
But these were all rejected by the council's ruling Conservative administration at a cabinet meeting.
The council said closing Culverhay would allow the authority to reinvest £1.75m in supporting other schools.
Councillor Chris Watt, the member in charge of education, said the council had taken note of all of the comments made in the consultation.
"This is the end of a process that started five years ago and all replies have been listened to," he said.