An estimated 200,000 teachers in England and Wales will take part in three days of industrial action as their dispute over pay continues.
Today, members of the National Education Union (NEU) in the north of England will walk out, with most schools expected to restrict access to pupils or fully close.
On Wednesday, union members in the Midlands and eastern regions of England will strike, with more walkouts in Wales and the south of England on Thursday.
Kevin Courtney, joint general secretary of the NEU, said: “I think a majority of schools will be affected by the dispute – some of them with full closures and many more with partial closures.
“Some secondary schools will be completely closed, others will have particular year groups in and a similar pattern in lots of lots of primary schools.”
Education Secretary Gillian Keegan said: “As a government, we have made a serious offer to the leaders of the National Education Union and Royal College of Nursing: pause this week’s strikes, get round the table and talk about pay, conditions and reforms.
“It is hugely disappointing the NEU has thus far refused this serious offer and has not joined the Royal College of Nursing in calling off strikes.
“Instead of sitting round a table discussing pay, the NEU will once again cause disruption for children and families.
“Children deserve to be in school, and further strike action is simply unforgivable, especially after everything children have been through because of the pandemic.”
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Mr Courtney said: “I think the government is fundamentally mistaken in thinking that industrial relations are solved by telling people you can’t go on strike if you want to talk to us.
“We are willing to meet at any time, any place and we would really hope that she does meet with us after these regional strikes and comes up with something serious that is an offer that we can put to members.
“That’s what we would want in an ideal world, to find a solution that means we don’t go ahead with those strikes in March.”
More national walkouts are due to take place in England and Wales on 15 and 16 March.
On the first day of strikes by NEU members – 1 February – Department for Education data suggested that 44.7% of state schools in England were open but restricting attendance, while 9.3% were closed.
Only 17.4% of secondary schools reported being fully open during the teacher strikes, compared with 52.1% of primary schools.
Teachers and school leaders in Northern Ireland went on strike for 12 hours last week as part of their pay dispute and teachers in the Educational Institute of Scotland (EIS) and NASUWT unions will also start a wave of national strikes on Tuesday.