NAPLAN's transition from pen-and-paper testing to online testing promises to provide better results and "a faster turnaround of information":
But in the first of a three-year rollout, some say it's the online test that causing a delay in the release of the results.
The Australian Education Union says the setback has been prompted by questions over whether the data is credible.
The Union's President, Correna Haythorpe, believes the results of online tests cannot be mapped fairly against the pen-to-paper exams.
Of the one million students in years three, five, seven and nine assessed this year, around 200,000 took the standardised tests online.
Ms Haythorpe says the Australian Curriculum, Assessment and Reporting Authority, ACARA, was due to publish a summary of the preliminary NAPLAN results last Wednesday.
But reports suggest that after seeing their students' test scores, some state education principals raised concerns about whether data between the new online and traditional written tests can be compared.
NAPLAN Online uses what it calls a 'tailored test design' where, as students progress through the test, the questions adjust to match their abilities.
For example, a child who is struggling will be offered questions they are more likely to be able to answer, while students who take the paper test all receive the same questions, regardless of their achievement level.
ACARA insists data analysts and measurement advisory experts have told them the data are valid and comparable.
In a statement, ACARA CEO Robert Randall says despite reports of a delay, the NAPLAN results are "on track to be released soon," adding that "ACARA expects this will be within coming days."
But Correna Haythorpe is not convinced, and says there are widespread concerns with the online component of the test.
