It follows a series of work stoppages in recent year over pay and conditions
Secondary school teachers will be balloted again on industrial action this month, in their long running row over pay and conditions.
The Association of Secondary School Teachers Ireland (ASTI) said the government has failed to address their concerns over the new Junior Cert and equal pay for equal work.
At a media briefing in the run up to a crucial ballot by members, ASTI President Ed Byrne accused senior Department of Education officials of having threatened the union's leadership with "as yet unseen and unknown measures" against teachers, if proposals aimed at ending the union's dispute with Government were rejected in the forthcoming ballot.
ASTI President Ed Byrne said the ASTI "does not respond well to threats".
"There is a possibility for further strikes because the 80% mandate from the last ballot was up to and including strike action", he said.
However, Mr Byrne added he is acutely aware of the position of parents and students, and said ASTI members may "realign the focus of industrial action" as a result.
The two main areas of contention remain entry-level pay for teachers and proposed Junior Cert cycle reforms.
"The proposals did not deal adequately with the equal pay for equal work", he said. He went on to say that the proposed Junior Cert cycle reforms are "not fit for purpose".