Almost a fifth of all Leaving Certificate estimated grades are due to be downgraded under changes to the calculated grades system, the Government announced.
Education Minister Norma Foley said just under 17% of grades calculated by schools would be reduced after she asked her Cabinet colleagues to approve changes to the system.
Some 4% of grades provided by the schools will be increased.
The number of extra higher education places being made available in the autumn has risen to around 2,600, after a further 1,250 were confirmed on Tuesday.
Taoiseach Micheal Martin said the results system was “robust and fair”.
Calculated grades are being issued for students who were unable to sit exams this year due to the coronavirus pandemic.
More than 61,000 Leaving Certificate students are eligible to receive calculated grades.
They will be issued to students on September 7.
The results will be based on a combination of estimated grades by teachers and a national standardisation process.
But Ms Foley said she had “serious concerns” about the use of school by school historical data and that the changes were designed to ensure students from disadvantaged areas were not treated unfairly.
“In other jurisdictions it had led to accusations that students attending disadvantaged schools in those jurisdictions were at risk of being treated unfairly or subjected to what was called a postcode lottery,” she said.
Ms Foley said having considered the effects and impacts of the current standardisation model, she had decided that the standardisation model should not include school by school historical data on the Leaving Certificate performance in schools in the previous year.
In making these changes, greater emphasis has been placed on the schools' estimated marksEducation Minister Norma Foley
She said: “In making these changes, greater emphasis has been placed on the schools’ estimated marks.”
Ms Foley added: “Overall as a result of standardisation, over 83% of grades across all levels are either unchanged or increase from the school estimated grade.
“In Deis schools, that figure is over 86%. This demonstrates the respect that the process has had for teachers and schools’ judgment about their students’ performance.”
The calculated grades system was introduced as an alternative grading system for students after the Government in May announced the Leaving Certificate examinations would not go ahead as planned in June.
The minister described it “as the best possible system under the current circumstances”.
But she acknowledged the system was “not perfect”.
“If we could have run a set of Leaving Certificate examinations safely for all 61,000 students, we would have done so,” she said.
Mr Martin said the Government had responded to concerns about using the past performance of schools as part of the standardisation process.
“We want to do everything we can to make sure that despite the extraordinary circumstances the class of 2020 has every chance to reach their full potential,” he said.