Scotland’s second largest teaching union is to ballot its members next month on taking industrial action over “excessive” workload.
The Scottish Secondary Teachers’ Association (SSTA) said the vote would take place between 14 and 30 September.
Another teaching union, the EIS, began a partial work to rule in June over workload related to new qualifications.
The Scottish government said it was committed to reducing workloads.
Education Secretary John Swinney has told teachers he is “absolutely committed” to addressing the issue of excessive workload.
On Monday, he issued new guidance to schools on the Curriculum for Excellence, saying it was designed to cut down on bureaucracy.
SSTA general secretary Seamus Searson welcomed Mr Swinney’s efforts but said action over the burden of new qualifications was not being taken fast enough.
He said: “The SSTA wishes to acknowledge and welcome the deputy first minister’s determination to declutter the work of teachers and allow them to focus on teaching and learning in our battle of ‘closing the attainment gap’.
“However, the SSTA view is that teacher workload has and is unlikely to be significantly reduced in the current session, especially in the area of national qualifications and therefore, a formal ballot is necessary to protect its members.”
SSTA president Euan Duncan added: “Much of a teacher’s time is now taken up with SQA assessments and verification of assessments within their school and local area.
“Should any teacher decide to keep their working week within the ‘working time agreement’, the reality is that they would be unable to develop the necessary resources for learning and teaching”.
A Scottish government spokesman said: “Given that we are taking steps to address the issues, industrial action by teachers would not be in the interests of anyone, least of all children and parents.
“The issues and concerns being raised by the teacher unions are being addressed. We have set out the various actions we are taking to tackle bureaucracy and free up teachers to teach, and we are already actively considering further measures.
“We are committed to reducing teacher workload and continued engagement with the profession will play a critical role in making this happen.
“We urge the unions to work with us to ensure our teachers feel supported and empowered to deliver an education system that gives all young people the chance to reach their potential.”