Teachers will ballot for strike action after outright rejecting the Government's controversial adademies plan.
Members of the National Union of Teachers (NUT), meeting at their annual conference in Brighton, voted overwhelmingly against what they consider to be the privatisation of the education system.
NUT executive member Ian Murch said the measures would see "schools stolen from their local communities".
He said: "We will stand up for pupils, for parents and for teachers, and we will lead the campaign for sanity. We will fight the forced academisation of our schools.
"We will fight for what is right and we will fight until we win."
Members voted against the Government's education white paper, and also agreed an amendment to ballot for strike action.
This is likely to include proposals for a one-day strike in the summer, as well as potential for further strikes, should members agree.
Members heard the academisation plans represented a "top-down dismantling of the English education system", and were distracting from the real issues facing schools - such as workload and funding.
Fellow executive member Hazel Danson described the plans as "a wilful act of recklessness".
But, the NUT's collective defiance may yet fall on deaf ears in Whitehall, after Education Secretary Nicky Morgan ruled out the prospect of a Government U-turn over academisation.
She told the NASUWT conference in Birmingham on Saturday there would be "no pulling back" and "no reverse gear" on the Government's education reforms, including the controversial roll-out of academy schools in England.
Support for academisation - which will force 17,000 state schools in England to become privately run academies within six years - has been hard to find from teaching staff, who staged marches around the country on Wednesday in defiance over the plans, announced in the previous week's Budget.
It comes after Labour's Jeremy Corbyn took to the stage as guest speaker on Friday afternoon - the first political party leader to do so in living memory - to condemn the "costly and unwanted" academisation at a time of "grotesque poverty".
Responding to the Department for Education's (DfE) white paper on the school reforms, the NUT's members were told: "Government decisions and mis-management is creating a crisis in education, involving the worst teacher shortages in living memory, insufficient school places, severe funding shortfalls and curriculum and assessment reforms that threaten to turn schools into exam factories.
"Conference wants the public to question why - instead of addressing these real and urgent emergencies - the Government plans to embark on a hugely expensive and unnecessary top-down reorganisation of state education in England."
Members are now expected to be balloted on the prospect of strike action, likely to be before the end of the summer term. Further strikes could then follow in the autumn term.