Teaching unions in Northern Ireland are considering joint strike action in late February following the half-term break, BBC News NI understands.
Union members are already taking co-ordinated action short of strike in schools.
Teachers in the NASUWT, INTO, UTU and NAHT unions had previously voted for the option of a walkout.
However, teachers in the National Education Union (NEU) are also now going to be balloted for strike action.
In an email to NEU members, the union's Northern Ireland secretary Mark Langhammer said if they voted to strike, "the first possible action could be in week starting 20 February".
"However, as any action will be co-ordinated with other unions it is likely that a 'Day of Action' may be called in the week following half-term break," his email continued.
