The Labour Party says the new predictive grades model for the Leaving Cert isn't fair on some students.
Last week it was announced that the Leaving Cert was to be replaced with calculated grades.
The Department of Education says students' marks will also be adjusted to bring them into line with their school's overall average.
But Labour's education spokesperson Aodhain Ó Riordain says it won't be fair on exceptional students in disadvantaged schools.
"If you're an average student in a middle class school, versus an exceptional student in a disadvantaged school the average student is going to fare better from this.
'The data set from the students around you, or in previous years, is going to bring you up."
