The Irish Congress of Trade Unions (ICTU) expects to agree a system of performance-related pay with the Government at the end of next week, despite threats by two teachers' unions to leave the organisation if it does.
The Association of Secondary Teachers in Ireland (ASTI) and the Teachers' Union of Ireland (TUI) are both strongly against the move.
The 160-member central executive committee of the ASTI will meet this Saturday to consider leaving the ICTU, and a motion calling for a ballot of members in support of industrial action may also be taken.
The union is concerned about performance-related pay, but also an existing pay claim in which it says teachers have fallen behind nurses and gardai.
This claim is known as the "early settlers" claim because teachers settled earlier than other groups during the last national pay round.
At this stage the ASTI central executive committee is understood to be split on the next steps. The union's smaller standing committee has already voted in favour of leaving ICTU, and talks were taking place yesterday in an attempt to achieve a compromise before Saturday.
It would represent a sizeable blow to ICTU if the ASTI, one of the biggest public service unions in the State, decided to leave the organisation.
The ASTI president, Ms Bernadine O'Sullivan, declined to comment yesterday, but other sources said the vote could go either way.
The union's general secretary, Mr Charlie Lennon, is understood to be strongly against any move to leave ICTU.
The Teachers' Union of Ireland (TUI), through its president, Mr Joe Carolan, has also said it will leave ICTU if performance-related pay is imposed on it through the next national agreement.
Its executive meets tomorrow, although it is unlikely a vote will be taken on the ICTU issue at that stage.
At the Irish National Teachers' Organisation the approach to performance-related pay has not been hostile.
The general secretary, Senator Joe O'Toole, says performance-related pay, as he sees it, involves teachers who improve their performance, by obtaining extra qualifications or training, being rewarded financially.
However, the other two unions are afraid teachers will be judged individually by their school principal or some outside body.
Government sources have said they are not looking for a system based on individual assessment of teachers. Instead, they want teachers as a group to "sit down and take part in a process where they agree on ways to improve performance".
This would involve groups of teachers and their schools agreeing "in general terms" initiatives to improve performance, the sources said.
But for many teachers the phrase throws up the spectre of individual inspections of their work and, more crucially, of the exam results achieved by their pupils.
However, Senator O'Toole said that whatever form of performance-related pay might come into play at the national talks it would not involve "payment by results". In an editorial in the INTO's magazine, inTouch, he writes: "Performance-related pay focuses on issues like upskilling, extra workload, additional qualifications, new responsibility, taking on new challenges, and many more."
He adds: "There is also the need to create opportunities for staffs to be able to earn more from doing what they are qualified to do. Put that way it does not sound as threatening. Of course, there are all sorts of difficulties attaching to it. But we need not be frightened, just careful".
However, members of the ASTI and the TUI do not accept these assurances, and many of them believe some kind of individual appraisal could be brought in by the back door of the national pay talks.
Senator O'Toole has ruled this out and said teachers will be able to vote on anything that comes out of the talks.
Either way the two sides of this argument will be seeking to influence the broader trade union movement and, more importantly, the Department of Education and Science in the next few months.
The two meetings on Friday and Saturday will give some indication of the feelings of teachers about the issue. Many of them have yet to come to a final position on this acrimonious subject. But it is likely their full-time officials will know their views when the teacher conferences take place later this year.