This year's Junior Certificate results will be issued on 4 October, more than two weeks later than usual.
The State Examinations Commission says the delay is due to an additional workload caused by the reconfiguration of this year's Leaving Certificate examinations.
Those changes were introduced in order to speed up procedures for students who have appealed the results of their Leaving Certificate exams.
The SEC says that a delay to the issuing of the Junior Certificate results is necessary to allow them to prioritise this work.
Sinn Féin's education spokesperson Donnchadh Ó Laoghaire has said that the delays are unacceptable.
"It is simply unacceptable that students who sat their Junior Cert in June of this year will not get their results until at least October.
"Many students put a lot of time and effort into their state exams, and it must be extremely disappointing for them to discover that they will not get their results next Wednesday as expected.
"It undermines the seriousness of state examinations and is unfair to all affected. I expect the Minister [Joe McHugh] to provide clarity on this issue as a matter of urgency," Mr Ó Laoghaire said.