A HEAD teachers' union has begun balloting its members on strike action for the first time.
The NAHT said the past eight years had placed school leaders under intolerable strain.
Continued industrial action by teachers, coupled with a lack of a functioning executive, pushed members "to their limit".
The union represents principals and vice-principals in about two-thirds of the north's schools.
NAHT(NI) President Geri Cameron said school leaders' efforts had been taken for granted and members felt over-worked, under-valued and without protection.
From today, members will be asked to indicate their support for either a strike or action short of strike. The ballot will be open for two-weeks, closing on September 30.
"It is time for action. Members will be sent ballot papers to their home address and they must indicate if they are willing to participate in strike action and action short of strike," Ms Cameron said.
"Any action taken by NAHT(NI) members will be directed towards the employers who have failed to end the dispute which focuses on workload, the inspection process, consultation and support for schools. We will work towards minimising any impact upon learners and their families."
Ms Cameron added that the union remained open to further negotiations with employers "to find a resolution that will positively impact on the work life of school leaders".
The north's four main teaching unions are involved in long-running industrial action over pay.
