School strikes: NUT and NASUWT vote for more action over pensions
The two biggest teachers' unions have voted for strikes which could hit schools across the UK this summer and autumn.
The National Union of Teachers voted for more strikes co-ordinated with other unions protesting against cuts to public sector pensions.
Earlier, the NASUWT backed industrial action, including strikes, over what it said were threats to state education.
The government says strikes benefit no-one and damage children's education.
The NUT says it will try to avoid taking action in the summer exam season.
However, the union aims to stage a one-day national strike before the end of June and to look at taking further regional action in the summer.
These would affect England and Wales, although the union will hold talks with other unions in the UK with a view to co-ordinating action, its leaders said. Pensions changes affect the whole of the UK.
After the vote the NUT's general secretary Christine Blower said: "The overwhelming majority of teachers and their organisations have clearly rejected the government's plans for teacher pensions changes.
"Their determination to continue the campaign is absolute.
"Our members do not want to work longer and pay more to get less."
Teachers' unions took part in two national strikes with other public sector workers over pensions last year, in late June and November.
Two-thirds of UK schools were closed by the November action.
The two big teachers' unions are holding their annual conferences this weekend.
'Good as it gets'
The government says public sector pension reforms are vital and that the present deal is as "good as it gets".
A spokeswoman for the Department for Education said: "Strikes benefit no one and they damage children's education.
"The cost to the taxpayer of teacher pensions is already forecast to double from £5 billion in 2006 to £10 billion in 2016 and will carry on rising rapidly as life expectancy continues to rocket."
Earlier, the NASUWT backed an escalating campaign of industrial action over what it called "ideologically driven attacks" on state education.
That could mean strike action in schools in the autumn.
The union has been on a work-to-rule since taking part in the autumn national strike.
At the conference in Birmingham, Brian Cookson, the NASUWT's national treasurer, called for a campaign of industrial action - up to and including strikes.
He told the conference that "education is on the front line facing this attack" on the public sector - and called on them to back a motion which brought together concerns about pay, teachers' rights and "safeguarding state education".
Mr Cookson said the calls for "school autonomy disguised the true aim of academy chains taking over vast numbers of schools, replacing the democratically accountable local authority system".
The motion passed unanimously at the conference accused the government of a "vicious assault" on teachers.
Later, a spokeswoman for the Department for Education said: "It is absurd to say our school reforms are a 'vicious assault' on the teaching profession. They are all about putting children first and raising standards.
"We are putting power back into the hands of talented heads and teachers - allowing them to get on with raising standards without interference from Whitehall or politicians."