A slip in NAPLAN results has added to calls for reform.

National preliminary figures for the 2019 nationwide standardised tests show that while primary school students saw a small rise in average scores in some areas, results were stagnant or even went backwards in other categories.

Year 7 and 9 students slid backwards on the baseline score set just over a decade ago for writing, while Year 9 students' scores were flat across the board.

Federal Education Minister Dan Tehan concedes that there is “further work to do” to raise literacy and numeracy scores.

The results have fuelled critics of the assessment scheme. Three states are already preparing formal reviews of the tests.

Victorian Education Minister James Merlino says Year 9 is “the most difficult” cohort to engage.

“If they don't see the relevance in the test, they're not going to take it seriously,” he said.

He has proposed linking the tests to a literacy and numeracy certificate that Year 9 students could show would-be employers. The minister believes this would boost engagement.

“We need our Year 9 students to think; ‘OK, this test means something, I'm going to give it my best shot, and I'm going to give it my best shot because I'm going to get a certificate that's going to go into my careers portfolio’,” he said.

Victorian is one of the states set to review the NAPLAN scheme, having established an advisory committee including principals from government, independent and Catholic schools.

New South Wales and Queensland are also running reviews of the system, which has been delivered in its current form for more than a decade.

Any recommendations coming out of the states’ reviews would go to the Australian Curriculum, Assessment and Reporting Authority (ACARA) for approval.

The Australian Education Union (AEU) has used the results to renew its criticism of online NAPLAN testing.

“Despite whatever story ACARA tries to spin, this data is so seriously compromised it should not be relied upon by education departments, schools, parents, and the broader community,” AEU acting federal president Meredith Peace said.

“Teachers and principals cannot trust NAPLAN or the results it has produced.”

Mr Tehan has defended the system.

“Let's not blame the tests. Let's make sure that we understand what the results are and where we need to put the work in,” he said.

ACARA CEO David Carvalho said there are some positive readings, like the increase in all student writing results compared to 2018.

“NAPLAN results for 2019 in writing have shown a pleasing improvement from last year, and it is a trend we would like to see continue, given the decline in recent years across all year levels,” Mr Carvalho said.