Teachers in England and Wales who are members of the National Education Union (NEU) will take part in walkouts on Wednesday which threaten disruption to more than 23,000 schools.
The walkouts, which could see more than 100,000 teachers go on strike, is the first of seven days of action planned by the NEU in February and March.
Teachers are joining university staff, train drivers, civil servants, bus drivers and security guards who will all strike on Wednesday in what is set to be the biggest day of industrial action in more than a decade.