Strikes will close most state schools in England and Wales for several days over the next two months if teachers vote this week for industrial action.
The National Education Union (NEU) has rejected a 5% pay offer and is expected to reveal the result of its strike ballot on January 16.
It is understood the NEU is planning several days of action from the start of February to the middle of March.
Two other teaching unions are balloting this week but NEU general secretary Kevin Courtney said the result was likely to be close.
