The State Exams Commission says it won't be possible to rerun last year's hybrid Leaving Cert model.
The Irish Times reports the cancellation of the Junior Cert in 2020 makes it "impossible" to give students a choice, as the information was seen as crucial in helping teachers grade them.
The Commission's now understood to be examining other contingency options.
Meanwhile the Labour Party's calling on the Education Minister to make a decision this week on what form the exams will take.
The party's education spokesperson, Aodhan O Riordain, says the situation's becoming intolerable for students.