Unions are set to appeal against a High Court decision which declared government changes to public sector pensions were legal.
Chris Keates, General Secretary of the NASUWT, the largest teachers' union, said that the decision would disappoint teachers and they would "lodge an immediate appeal".
"Hardworking serving teachers and their retired colleagues who have given a lifetime of service to children and young people were looking for justice in the face of a government decision which overnight slashed the value of their pensions. They will clearly be disappointed that the High Court has not found in their favour.
"They can however take heart from the fact that the judges were unable to reach a unanimous decision on all of the key issues put before the court. One of the judges did believe that the government had acted unlawfully.
"On this basis the NASUWT has today instructed our legal representatives to lodge an immediate appeal.
"The Union pledged at the outset to leave no stone unturned to protect the interests of teachers and will, therefore, seek to exhaust all possible legal remedies."
The NUT is also planning to appeal the ruling.
The government decided to change from using the consumer price index (CPI) to measure interest on pensions from retail price index (RPI) in June 2010- a move challenged by unions as unfair, and one which could cost public sector workers millions.
But lawyers for the coalition say CPI is "a more appropriate measure of changes in the general level of prices" and will save £6bn a deal.
The unions challenging the deal included the Fire Brigades Union,NASUWT, Prison Officers Association, Public and Commercial Services union, Unison and Unite, Prospect, the FDA, GMB, Police Federation, National Association of Retired Police Officers and the Civil Service Pensioners' Alliance.