Thousands of teachers are taking part on a one-day strike today in a continued row over pay, pensions and working conditions.
Tens of thousands of schoolchildren are expected to be affected by the walkout, which is taking place across four English regions.
The industrial action - the latest in a wave of regional strikes - has been organised by two of England's biggest teaching unions, the National Union of Teachers (NUT) and the NASUWT.
The Government has condemned the move, saying it is "disappointed" the unions have decided to strike.
The walkout will affect schools in 49 local authorities in East of England, the East Midlands, West Midlands and Yorkshire and Humberside.
NASUWT general secretary Chris Keates said: "The overwhelming majority of teachers in four regions will be on strike today.
"Strike action is a last resort, teachers have been left with no choice but to demonstrate their anger and frustration in the face of their genuine concerns being dismissed and trivialised."
NUT general secretary Christine Blower said: "No teacher takes strike action lightly but the intransigence of this Education Sectary has left teachers with no choice.
"We cannot stand by and watch our profession be systematically attacked and undermined. There needs to be a change in the Government's attitude to teachers and education."
A DfE spokeswoman said: "It is disappointing that the NUT and NASUWT are striking over the Government's measures to allow heads to pay good teachers more."
A recent poll found that 61% of those questioned backed linking teachers' pay to performance - a key Government reform currently being introduced - she insisted, adding that the survey also found that majority of respondents were opposed to the walkouts or thought teachers should not be allowed to strike.
"All strikes will do is disrupt parents' lives, hold back children's education and damage the reputation of the profession," the spokeswoman said.
The first regional walkout took place in the North West on June 27, and further strikes are expected to take place on October 17 in the North East, South East, South West and London.
Plans for a national one-day walkout before Christmas have also been announced by the two unions.
Today's action comes in the same week that workers in crown post offices went on strike in a row over jobs, pay and closures. Strike threats also remain within the fire brigade and over Royal Mail privatisation.