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.
Reopening schools
Meanwhile, the National Public Health Emergency Team's advice on schools not opening until September is not expected to change.
That's according to the Deputy Chief Medical Officer, amid growing calls for classes to resume as early as next month.
The WHO's Special COVID-19 Envoy says it's now time to think about re-opening schools, while the National Parents' Council is calling for classes to resume in June if it's safe to do so.
Deputy CMO Dr Ronan Glynn, says while they'll look at the impact of the restrictions on children, it's unlikely any phases of the reopening plan will be brought forward.
Speaking this evening, he said: "I certainly don't see any speeding up in terms of the phases.
"But we have been clear that we continue in particular to look at the issues that have arisen for children and parents in relation to the measures that have had to be taken to date."
