pposition parties have rallied against the Government's decision to press ahead with the traditional format of Leaving Cert exams.
Minister for Education Norma Foley said the profile of grades for this year will be based on that of last year.
The decision has received widespread criticism from opposition parties, who have called for a hybrid option of accredited grades and a written exam to be offered to students.
Sinn Fein president Mary Lou McDonald said the decision not to have that offer is "an appalling decision".
"It's a massive mistake not to allow a hybrid model or a blended model and to give a choice to students between traditional exams and calculated grades," Ms McDonald told the Dail.
"Students have been very coherently calling for choice, for a blended approach because it makes sense, because it is fair.
"This year's leaving cert students have had their entire senior cycle disrupted, fifth year and sixth year, by Covid-19.
"They've had to overcome massive academic challenges and that is before we even consider the incredible pressure on their mental health.
"Students faced two months of full closures last year, they had out of class education, which is not comparable to in classroom learning.
"Many struggled with the lack of devices, with Wi Fi connection issues and on top of all of that, they had the stress as young people living through a global pandemic.
"There were high levels of absence of students and teachers because of self isolation and infection that's had a massive impact.
"We know there are challenges in this but I don't accept that any of the challenges are insurmountable."
She called for Ms Foley to reverse her decision.
Recent weeks have seen calls for a rethink about how school exams are to be held in Ireland this year, amid concerns about the disruption students have faced.
Social Democrats co-leader Catherine Murphy said that students and parents are "extremely anxious, confused and angry" by the announcement on Tuesday.
"There have been lengthy school closures we know through illness with both teachers and pupils, and indeed been close contexts," Ms Murphy told the Dail.
"In addition, students whose education was seriously disrupted because of Covid did not experience the pandemic equally.
"Those ones who had who were lucky enough to have remote teaching during lockdowns don't compare with others who didn't even have broadband or a tablet to keep up with coursework."
Taoiseach Micheal Martin said an accredited grades system could not have been applied fairly because one out of four students did not do the Junior Certificate.
"Their data would not have been available for an accredited grades alternative," Mr Martin said.
"I haven't seen anybody put forward an alternative to that in any meaningful way.
"The minister has now opted to give a very, very wide choice in the written examinations to such an extent that most papers will have content caught by a third.
"Students should look to the paper of 2021 in terms of of a guide and also there will be full details in terms of syllabus and so on published in the coming days."
He said this year's Leaving Cert will be "dramatically different" and will represent a "dramatically widening" of choice compared to 2019 and 2018 exam papers.
"These significant changes will help students to take account of what has been a very challenging two years," the Fianna Fail leader added.
