A HALF-DAY strike by the majority of teachers in Northern Ireland will be held on February 21 amid the continuing row over pay and conditions.
Members of the INTO, UTU and NASUWT will take action from midnight until midday.
It is expected that many schools will close until midday, as most teachers in the north are represented by the three unions.
Gerry Murphy, INTO’s Northern Secretary, said teachers will "withdraw their labour from schools for the half-day before returning to their normal afternoon duties".
Unions have already been taking part in coordinated action short of strike in schools, which has affected meeting attendance and administrative tasks.
The NEU is currently balloting members on strike action, while the NAHT union is yet to confirm.
Mr Murphy said: "This crisis is such that all of the teachers’ unions at the Northern Ireland Teachers’ Council are totally united in respect of fair pay and while we, along with our sister unions, have announced this half-day of action, we once again call upon the different employing authorities, and the Department of Education, to engage with the Department of Finance to achieve a fair and just resolution through joined-up thinking and dialogue.
"While this action is a last resort for our members, they are at the stage where they feel they must escalate their stand against the underfunding education and de-valuing of the profession which has decimated their pay and continues to negatively impact on the quality of educational provision available to our young people."
Justin McCamphill from the NASUWT said: "Our members would rather be in school working with their pupils, but have had no option but to take this action in order to stand up for their right to a salary which reflects the skilled and difficult work they do and which enables them to weather the cost of living crisis".
Meanwhile, staff at Ulster University and Queen's University Belfast are due to take part in a series of walkouts across seven weeks.
The action by members of the University and College Union (UCU), which represents lecturers and support staff, is over pay, workloads and pensions.
It confirmed 18 days of action with more than 70,000 staff across 150 universities in the UK set to take part. The strike dates are February 1, 9, 10, 14, 15, 16, 21, 22, 23, 27 and 28 as well as March 1, 2, 16, 17, 20, 21 and 22.
The UCU said employers need to improve on a pay offer worth four to five per cent to avoid disruption, but the Universities and Colleges Employers' Association (UCEA) says the current offer is worth up to seven per cent.
UCU general secretary Jo Grady said: "A resolution can be reached, but that is in the gift of university vice-chancellors who need to urgently reassess their priorities and deliver a deal that benefits staff and students".
She said the UCU will be re-balloting members "to allow action to continue through the rest of the academic year" if a resolution is not found.
Raj Jethwa from UCEA said they are "asking the trade unions to consult their members over this pay offer rather than push them into striking that tries to target students".