The national school testing program is showing improving results among Indigenous students and students from multicultural backgrounds.

But Australian Curriculum and Assessment Reporting Authority's David de Carvalho has warned the current progression of Indigenous students still requires urgent support.

"If these rates of growth were to continue, we wouldn't see a closing of the literacy gap until some time in the next century."

“Even though these high rates of growth are something to take comfort in, it's still going to take too long to effectively close the gap in literacy and numeracy," he said.

He said the results this year show there is a lot of good work being done by indigenous students, their families and communities.

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NAPLAN tests are conducted for more than 1 million students nationally each year for years three, five, seven and nine.

READ MORE NAPLAN results show Australian students falling behind in writing

The latest NAPLAN results showed “cumulative” improvement in the reading and spelling of Indigenous students in years three and five and numeracy in years three, five and nine since 2008.

Education Minister Dan Tehan welcomed the “significant” gains for Indigenous students.

But he too said that more work is still needed to help Indigenous students reach the standards of non-Indigenous peers.

"There has been fantastic improvement in the results of Indigenous students but more needs to be done to close the gap, that is why the Morrison Government is making Indigenous education a focus of its efforts," he said.

The results also showed improvement in grammar and punctuation among Indigenous students for years three, five, seven and nine.

Furthermore, NAPLAN results displayed that Indigenous students were improving in areas at a faster rate than their Indigenous peers.

This included among year three Indigenous students where results improved by 7.4 per cent between 2008 and 2018, compared to 4.2 per cent for non-Indigenous students.

This growth slowed for high school students, but still followed the trend of faster progression among Indigenous students than non-indigenous students.

Year nine Indigenous students have improved results by 1.2 per cent since 2008, compared with 0.6 per cent for non-Indigenous students in the same year group.

The gap that still needs to be bridged included disparities in the mean scores for non-Indigenous students and their non-Indigenous counterparts.

At least 77 per cent of year three Indigenous students achieved at or above the national minimum standard in numeracy and literacy – this compared to more than 95 per cent of non-Indigenous students.

In year nine, 83 per cent of Indigenous students achieved at or above the national minimum standard in numeracy, and 71 per cent for literacy.

The national averages for Australia overall were that more than 90 per cent reached national minimum standards in numeracy and literacy.

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For students from a language background other than English the results showed improved reading in years three to five, grammar and punctuation - years three and seven, and numeracy in year five.

Mr David de Carvalho said the rate of growth overall among students was a lot slower for Year 7 and 9 students than at the primary school levels.

The report’s results showed no distinct statistical changes with the report from the previous year, according to the Australian Curriculum, Assessment and Reporting Authority.

A statement from the testing regulator reads that "there were no statistically significant changes in any of the NAPLAN test domains" compared with 2017 results.

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However, Minister Tehan highlighted a decline in writing skills from years five, seven and nine since 2011 as one troubling area that needs improvement.

“The decline in writing skills in years five, seven and nine since 2011 is concerning,” he said.

"But [the report] does show that we are seeing real improvements," he told reporters in Canberra.

The results still demonstrate that Australian children are reading and writing better than a decade ago.

There have been significant gains across some domains and year levels since the national literacy and numeracy over this period.