Leaving Cert students are being assured that they will not have their grade entirely decided by their mock exams.
Education Minister Joe McHugh says it will only feature as part of the process of predictive grading.
The Minister has also said a 'one size fits all' approach to re-opening schools won't work.
Earlier this month it was confirmed that the traditional written exams were being postponed, with students given the choice of accepting 'calculated grades' or waiting until a later stage to sit the exams.
Schools will tomorrow be issued with detailed guidance on the predictive marking system - setting out how teachers will be expected to grade students and the criteria they should use.
Minister McHugh today told the Dáil that a student's entire body of work in school will be looked at when they're graded under the new system.
He explained: "There is one issue on which I think it is important to be clear, [as] it has come up in a lot of the questions.
"The guidance makes it clear that the estimated mark is not based on a student's performance in any mock examination undertaken in their school or their junior cycle results.
"The estimated mark is informed by a teacher's professional judgement, and available evidence can be used to support the estimation of a mark."
According to the Government, teachers will only be able to factor in mock examinations 'with caveats' when determining grades, along with other school assessments such as summer exams.
Teachers will also be able to draw on the likes of classwork and homework when determining the grade.