The Department of Education has said it will slow down the pace at which a new programme covering the first three years of secondary education will be introduced.
It has also increased the amount of training that will be provided to teachers to enable them to teach the new curriculum.
The concessions were proposed at a meeting with teacher trade union representatives and other education bodies this afternoon.
The meeting was the first of a special working group established to address concerns expressed by teachers and others.
In a statement, the Association of Secondary Teachers' Ireland (ASTI) and the Teachers' Union of Ireland (TUI) expressed "grave disappointment" after today's meeting.
They said there was no genuine engagement on the issues of most concern to teachers.
The unions' executive bodies will now meet to decide on balloting members on non-cooperation with the implementation of the proposed changes.
Minister for Education Ruairi Quinn is determined to reform Junior Cycle education, but teachers and school managers have expressed great concern about schools' ability to deliver the changes.
At today's meeting, Department of Education officials said those concerns were legitimate.
They presented trade union and school management representatives with a number of concessions.
At least two additional days of training, on top of the three originally proposed, will be given to teachers in the new programme.
One of those days will involve schools closing to allow all staff to participate.
Addressing concerns around the pace of change, the next two years will see just two new subject specifications introduced - English and Science - as opposed to the four originally intended.
There were no firm proposals at the meeting on two key issues; a lack of resources in schools and concerns around school-based assessment.
But the department has proposed that sub-groups be established to look in detail at these two matters.
Schools are concerned that recent cutbacks and the loss of middle management posts in schools will hinder their ability to introduce the programme successfully.
While no firm proposal has been made on this, the department is proposing to establish a group involving school managers and the teacher unions to look at this issue.
On the question of local teacher assessment replacing what is currently a national qualification, department officials have pointed out that there will be quality assurance.
Earlier this week the name of the new exam to replace the Junior Certificate was announced. It is to be called the Junior Cycle Student Award.
The new programme aims to reduce the focus on a final exam and to allow more opportunities for independent as opposed to rote learning.
Speaking after today's meeting, ASTI General Secretary Pat King said: "In a series of bilateral meetings over several months, both ASTI and TUI had outlined their significant concerns over the proposed changes, including the threat to the standards and objectivity of exams at Junior Cycle level, the capacity of schools to implement the new Junior Cycle programme in the wake of a litany of cutbacks, and the potential of the programme to exacerbate inequalities between schools."
TUI General Secretary John MacGabhann said: "We have consistently stressed that change for which adequate preparation has not been made can cause lasting damage to the education system and particularly to individual students.”