Thousands of schools in England have been closed or are facing serious disruptions after teachers walked out in a row over pay, pensions and working conditions.
The industrial action - organised by the NASUWT and the National Union of Teachers - is being staged in the North East, Cumbria, the South West, South East and London according to Sky News.
NASUWT general secretary Chris Keates said that the "overwhelming majority" of teachers in each of these areas would be on strike.
She said: "No teacher has any wish to inconvenience parents or disrupt pupils' education, but this action is not the failure or due to the unreasonableness of teachers.
"It is the failure and unreasonableness of the Secretary of State (Michael Gove), who day-in, day-out is disrupting the education of children and young people through his attacks on the teaching profession."
The Government condemned the move, saying it was "disappointed" the unions had decided to strike.
A Department for Education spokeswoman said: "All strikes will do is disrupt parents' lives, hold back children's education and damage the reputation of the profession."
The unions are opposed to Government plans to allow schools to set teachers' salaries, linked to performance in the classroom, and argue that pension changes will leave their members working longer, paying in more and receiving less when they retire.
They also accuse the Government of attacking their working conditions, including introducing reforms that will allow schools to have longer school days and longer terms.
Research published earlier this month by the Varkey GEMS Foundation revealed that the British public think teachers should be paid around 15% more than their current salaries.
Almost three-quarters (74%) were in favour of performance-related pay for teachers, according to the study.
Regional strikes have already taken place in the North West on June 27, and in the East of England, the East Midlands, West Midlands, Yorkshire and Humberside on October 1.
Plans for a national one-day walkout before Christmas have also been announced by the two unions.
The latest action comes days after a major international report put England 22nd out of 24 western countries on literacy and numeracy.