Up to 17,000 secondary school teachers are starting industrial action today.
Members of the ASTI won't attend meetings outside school hours or take on additional duties as part of its dispute over the public sector pay deal. Teachers will refuse to hold planning and policy development meetings and in-service training unless it is during the school day.
The also ASTI said its members are being directed not to undertake any duties arising from vacant middle management posts unless they receive pensionable pay for the work.
The union says its members may also opt out of covering for absent colleagues - and won't participate in training for the new Junior Cert.
The ASTI has told its members they face explusion from the union if they don't take part.
The decision was announced last week after leaders of the ASTI met to discuss enforcing a ballot of teachers in favour of the action, up to and including a strike.
The union said while teachers are anxious not to disrupt students’ education, the vote had been two to one in support of the action.
The ASTI said its members are being directed not to undertake any duties arising from vacant middle management posts unless they receive pensionable pay for the work.
Other teaching unions, including the INTO and the Teachers’ Union of Ireland, have supported the Haddington Road agreement which will change pay and working regimes across the public service.