The Education Minister Joe McHugh has confirmed the 2020 Leaving Cert has been cancelled.
Instead, students will be offered the option of calculated grades - or sitting written examinations "at a later date".
The decision was taken following an assessment of public health advice.
Minister McHugh said: "My desire had been to allow students to undertake the written and practical examinations in July and August but I have compelling evidence, based on medical advice and other assessments, that the Leaving Certificate examinations cannot be held in a reliable and valid manner, nor in a way that would be equitable for students."
"This decision is taken with the best interests of students at heart.
"I have a responsibility to find a fair way to address the disadvantage that some students are facing and the impact a lack of time in school has had in recent weeks."
There'll be no Leaving Cert fee this year, with all exam fees paid to be refunded.
Teachers will be asked to provide "a professional judgment" of each student’s work - which will be subjected to an in-school alignment process to ensure fairness.
The school principal will also approve the estimated scores.
The Minister for Education and Skills has announced that Leaving Certificate 2020 is postponed and students are being offered a system of Calculated Grades, with State certification.
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A special unit is being set up in the Department of Education to process the scores provided by each school and operate national standardisation.
And the department will finalise the grades for each student, which will be issued individually as close as possible to the traditional date.
They'll also get a formal certificate from the State and have the right to appeal.
This'll involve checks on school-entered data, correct transfer of that data to the department; a review that it was correctly received and processed by the department; and a verification of the department’s processes by independent appeal scrutineers.
“The system being put in place will allow a young person to progress to the next stage of their life in a timely fashion", Minister McHugh added.