A second teaching union is to ballot its members on taking industrial action over their workload.
The Scottish Secondary Teachers’ Association (SSTA) said an indicative ballot showed the majority of its 8,000 members supported taking action.
Last week, Scotland’s largest teaching union, the EIS, said its secondary school members would go on a partial work to rule.
The Scottish government said it was committed to reducing workloads.
The SSTA said it had “no option” but to move to a formal ballot after its indicative ballot showed 91% of respondents were prepared take industrial action short of strike action, while 64% were prepared to take strike action if necessary.
General secretary Seamus Searson said workload has been “the major issue” for teachers for a number of years.
He said recent guidance from teaching bodies Education Scotland and the SQA had not addressed the problem.
Mr Searson said: “In the short term, SSTA members across Scotland are asking for some action to be taken to address the workload that is demoralising teachers in the 2016-2017 qualification cycle.
“The SSTA acknowledges the statements that John Swinney, cabinet secretary, has made on cutting teacher workload but teachers in schools have had promises made in the past which have not come to fruition.
“The SSTA hopes action can be taken quickly to resolve this dispute.”
The Scottish government said it was taking steps to address the issues and industrial action by teachers “would not be in the interests of anyone, least of all children and parents”.
A spokesman said: “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.”