The Department of Education has found two errors in the Leaving Certificate calculated grades system, Taoiseach Micheál Martin has told the Dáil.
It is understood the errors will affect about 6,000 pupils, or 10% of candidates.
When schools closed in March due to the Covid-19 pandemic, all Leaving Cert students were given the option of accepting ‘calculated grades’ or sitting written exams at a later date, when it is safe to do so.
Calculated grades were totted up the same way for all students, whether they have completed the established Leaving Cert, Leaving Cert Applied, or the Leaving Cert Applied Programme.
Detailed guidelines were given to schools on how calculated grades should be issued. It’s a four-step system.
First, teachers were asked to use their professional judgement to give each student an estimated grade and a class ranking in their subject.
These marks were then considered by other teachers in the school to see if the process has been correctly followed.
It was then reviewed by the school principal.
Once the school principal was satisfied that the process has been followed correctly, the data was then submitted to the Department of Education.
Education Minister Norma Foley said an error in the calculated grading system will "not disadvantage any student" after she revealed 6,500 students are impacted.
Ms Foley confirmed there were two errors in the calculated grades system.
"These are errors that should not have occurred, however, this will not disadvantage any student," she said.
The fault was identified by a contractor, paid €160,000 to oversee the function of predicted grades, on Tuesday of last week.
The contractor informed the Department of Education immediately but the public was only made aware of the mistake today after a debate in the Dáil.