Latest: The Association of Secondary School Teachers (ASTI) plans to ballot for strike action if the INTO does the same.
The Association of Secondary Teachers in Ireland's taken the decision at a meeting of its Central Executive Council.
It is after Government proposals on new entrant pay steps were rejected by both unions.
ASTI General Secretary Ciaran Christy says they are backing their colleagues in the INTO.
"We have made a decision that we will ballot our members in parallel with our other union the INTO who are currently considering a ballot proposal as well," said Mr Christy.
Earlier: The Association of Secondary School Teachers is meeting today to discuss its next moves on pay equality for new entrant teachers.
It's after members rejected government pay proposals for those who entered the profession after 2010.
58% of ASTI members voted in the November ballot, with the plan being rejected by a margin of 6%.
As part of the Public Service Pay Plan, newer entrants would have received an average pay increase of over €3,000.