Schools may have “no choice” but to close their doors to pupils during strikes, the leader of headteachers’ union, NAHT, warned today after teachers in England and Wales became the largest group of public sectors so far to vote overwhelmingly in favour of industrial action.

In the profession’s biggest-ever walkout, over 250,000 teachers, who are members of the National Education Union, will swap the classroom for the picket line for seven days in February and March, in protest over what the NEU has branded “a toxic mix of low pay and excessive workload”.

Gillian Keegan, the education secretary, is set to stage urgent meetings with teaching unions on Wednesday.