SCHOOLS face closing down within days as teachers' strikes cause chaos in the education system.
Education Secretary Gillian Keegan has warned of "unnecessary disruption" caused by walkouts.
Teachers are launching a string of strikes across the UK, affecting seven days in February and March.
Ms Keegan wrote to union bosses at the National Education Union (NEU) asking them to "encourage" members to inform their head teachers if they plan to join the strikes.
She said notice of which staff would be walking out would help to ease disruption and allow heads to "take important operational decisions to protect children's learning."
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While she acknowledged there was no obligation for staff give such notice, she added: "I understand the importance of maintaining teachers' right to strike, but I hope this important right can be protected whilst minimising the impact on children - especially in the context of the disruption they have faced due to Covid.
"Your co-operation would help ensure our dispute does not cause additional and unnecessary disruption."
However, Mary Bousted, joint general secretary of the NEU, said heads should prepare for action by all union members in their school.
In her response to the Education Secretary's letter, she said: "They should plan on that basis - that the members of the union will follow the union's request to withdraw their labour on that day.
"We don't want individual members to be put under pressure and be intimidated."
The union expects more than 150,000 of its members to take part, with over 20,000 schools affected.
Teaching staff in England and Wales are set to stage their first walkout on Wednesday February 1.
Then, strikes will go ahead on a regional basis on February 14 and 28, and March 1 and 2.
Finally, nationwide walkouts in England and Wales will take place on March 15 and 16.
The Government has asked schools to try and remain open, but the decision lies with head teachers in England, local councils in Scotland, and head teachers in consultation with local authorities in Wales.
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Parents and guardians are entitled to time off if normal arrangements are broken, but whether or not they are paid for this is up to their employer.
Ms Keegan is expected to meet representatives of the NEU and other education unions to discuss issues including pay and workloads on Monday.
A full list of planned strikes by area can be found here.
