The Teachers Union of Ireland wants the implementation of the new Junior Cert cycle to be postponed.
From September, pupils will study for the JCSA - or Junior Cycle Student Award. This year's intake of first year students will be the last to sit the old-style Junior Cert.
The union says the practical details of the changes have yet to be worked out and time is running out.
The Minister for Education Ruairi Quinn outlined today the exam will be rebranded the Junior Cycle Student Award.
Minister Quinn says the new system will put students, rather than exams, at the centre of the three-year process.
President of the TUI Gerard Craughwell says the changes are being rushed and teachers will not be able to cope with the increased workload.
The minister said: "The overhaul of junior cycle is long overdue and much needed.
"However, I do acknowledge that many teachers have legitimate concerns about how these new changes will be introduced in schools.
The minister said a new working group on Junior Cycle Reform will meet for the first time this Friday, January 17.
"This working group will be a forum where the concerns of the partners can be heard and addressed over the next number of months and years," he added.
The group is made up of representatives from the teacher unions, the ASTI and TUI, management bodies, parents, the National Council for Curriculum and Assessment and the Department of Education and Skills.