The Associations of Secondary Teachers, Ireland have told its members the Leaving Cert proposal cannot be enforced.
The State exam has been pushed back from its traditional start date at the beginning of June, to either late July or early August.
The union says teachers will not be required to do anything to prepare students ahead of the rescheduled exams.
The ASTI says it has a number of concerns and need clarification from the Department of Education.
However, Seamus Lahart, President of the Teachers Union of Ireland, says he will be asking his members to help students prepare for the exams.
"We have considered the Minister's request, particularly that we engage with students for two weeks during the month of July and we are asking members to engage in the process as a whole school response to meet the needs of our students.
"I am proud of teachers so far in the efforts they have made in extraordinary circumstances," he added.
