The two biggest teachers' unions have threatened co-ordinated strikes in the autumn against Government "attacks" on jobs, pensions, workload and pay.
The National Union of Teachers (NUT) and the NASUWT announced a "historic agreement", in response to the serious concerns teachers have about the way the Government is "undermining" the education system.
The two unions, which represent 85% of teachers in England and Wales, said their members were facing attacks on their working conditions, workload, pensions, pay and jobs.
The unions said they intend to mount an "unprecedented" joint campaign on these issues.
"Should the Government refuse to take the current opportunity to negotiate sensible arrangements which protect teachers and defend education, then it is our intention to move to escalate industrial action, including jointly co-ordinated strike action and action short of strike action in the autumn," said a joint statement.
NASUWT general secretary Chris Keates said: "Since the Government came into office, there has been a relentless and unprecedented assault on teachers' pay and conditions of service. This assault on teachers is damaging standards of education.
"Our two unions, which represent the overwhelming majority of the teaching profession, are united in our determination to defend education by protecting teachers."
NUT general secretary Christine Blower said: "Occasionally saying we have the best generation of teachers we've ever had in no way compensates for the onslaught of attacks and threats to pay, pensions and working conditions."
The unions wrote to Education Secretary Michael Gove to seek urgent discussions about the "enormous threats" to teacher morale and the education system itself. They called on Mr Gove to reach agreement before the start of the next academic year if industrial action is to be averted.
Officials said teaching is now in "crisis", with growing numbers considering quitting and virtually everyone opposed to Government policies.