A guidance counsellor says holding a Leaving Certificate exam of some form is 'absolutely essential' for students.
It comes as more than 2,200 pupils are receiving marks from the deferred Leaving Cert exam last year.
They will be able to access their marks online from midday.
Nearly 40% of students are getting higher grades from the deferred exam, than they were offered in predictive grades.
Students who earn more points than in the calculated grades will have the option to start a new, higher-point course in September.
Brian Mooney, who is also editor of the Education Matters yearbook, told Newstalk Breakfast the system used last year did not work as it should have.
"It shows that no matter what system we decide on for this year, having a Leaving Cert exam of some format - at some point - is absolutely essential".
He said there is an issue around using class rankings to weigh results.
"There's a problem, Ciara that nobody's mentioning... and that question is ranking.
"Last year the teachers were asked in May to give grades to their students, and they were asked to rank them.
"The Department of Education used a mechanism - the only standardised measure they had last year was the Junior Cert result of the students of 2020."
"So effectively, the teachers were not aware of the value of the class ranking.
"They were awarding grades - but actually when it came to it - the academic ability of the class, calculated based on their Junior Cert results, and the class ranking was determined who got the H1s and who didn't".
"But they were told that the students would never see that.... but what happened effectively was, that under Data Protection, everybody got to see them.
"Therefore, in small rural communities, students therefore knew that the teacher ranked them as number eight".
He added: "You can't run an assess grade process unless the unions buy into it.
"That's why we're hesitating, that's why there's a meeting this afternoon in which the unions are at the table.
"The Government can't proceed - the Cabinet Sub-Committee's recommendation to full Cabinet - cannot proceed unless you get the unions on-side".
"They both came out yesterday with coded messages basically saying 'We want an exam' - what was really being said in many ways was 'We don't want rankings because we don't want to go back to where we were last year'".