Every year in Australia, the National Assessment Program - Literacy and Numeracy (NAPLAN) results show Indigenous school students are well behind their non-Indigenous peers. Reducing this disparity is a vital part of Australia’s national Closing the Gap policy. The tenth Closing the Gap report will be published on Monday.

Unfortunately, the relevant Closing the Gap target – the proportion of students meeting National Minimum Standards (NMS) in NAPLAN - obscures the scale of the challenge. For some groups of Indigenous students, the difference is more a gulf than a gap.

Using an updated version of our equivalent year levels metric, introduced in Grattan Institute’s 2016 report Widening Gaps, we estimate year nine Indigenous students in very remote areas are:

five years behind in numeracy

six years behind in reading, and

seven to eight years behind in writing.

In other words, the average year nine Indigenous student in a very remote area scores about the same in NAPLAN reading as the average year three non-Indigenous city student, and significantly lower in writing.

But it would be a big mistake to see this only as a problem for isolated outback communities. Most Indigenous students live in cities or regional areas. So, even though learning outcomes are worse in remote and very remote areas, city and regional students account for more than two-thirds of the lost years of learning.

What the current metrics say

Three of the seven Closing the Gap targets relate to school education. They cover year 12 completion, school attendance, and literacy and numeracy.

The 2017 Closing the Gap report indicated Australia is on track to halve the gap by 2020 for year 12 (or equivalent) attainment. We are off target for school attendance, with no meaningful increase in Indigenous attendance rates in the past three years.

Read more: Radical rethink of Closing the Gap required, despite some progress

The final target is to halve the gap for Indigenous children in reading, writing and numeracy by 2018. As of last year, the only national target on track was for year nine numeracy, while close to half the measures were on track at the state and territory level. But even this picture is misleadingly optimistic.

The case for a new target

Measuring the gap using national minimum standards has two main problems. First, it ignores the difference between students who just meet the minimum standard and those who excel. Second, the standards themselves are set too low. A year nine student can meet the numeracy standard even if they’re performing below the typical year five student.

Our equivalent year level metric addresses these issues, and is much easier to interpret.

So what does the data say?

The gap grows as students move through school

At a national level, year nine Indigenous students are on average three years behind non-Indigenous in numeracy, 3.4 years behind in reading, and 4.2 years behind in writing.

Indigenous students are three to four years behind by Year 9

Mean NAPLAN scores from 2010 to 2017 (2011 to 2017 for Writing) translated to equivalent year level (EYL) using an updated version of the methodology in Widening Gaps (2016). The EYL scale is based on the average performance of metropolitan non-Indigenous students over 2010-2016.

The gaps have grown since the students were in year three, when Indigenous students ranged from being on average 1.2 years behind in numeracy to just under two years behind in reading and writing.

Indigenous students make on average about two years less learning progress from year three to year nine - a substantial progress gap.

The bulk of the lost learning is in the cities and the regions

Year nine remote Indigenous students are 4.1 years behind metropolitan non-Indigenous students in numeracy, 4.6 years behind in reading, and six years behind in writing.

Very remote Indigenous students are still further behind - 7.7 years behind in writing.

Regional and remote Indigenous students are even further back

Mean NAPLAN scores from 2010 to 2017 (2011 to 2017 for Writing) translated to equivalent year level (EYL) using an updated version of the methodology in Widening Gaps (2016). The EYL scale is based on the average performance of metropolitan non-Indigenous students from 2010-2016.

But year nine gaps are still about three to four years for Indigenous students in metropolitan and regional areas, which is where 80% of Indigenous students live. In fact, our analysis shows cities and regions contributed about 60-75% of the national gap in 2017.

There are some signs of improvement…

Since 2010, for Indigenous students:

most states have shown big gains in year nine numeracy (worth up to nine months of extra learning), and Queensland has improved the most in year three and five numeracy

the five big states (NSW, Victoria, Queensland, WA, and SA) have improved reading outcomes in years three, five and nine, although Tasmania, ACT and NT have generally stagnated, and

writing results have generally gone backwards - as have non-Indigenous results in writing.

Across writing, reading and numeracy, metropolitan Indigenous students have generally improved more than regional or remote students. A noteworthy exception is very remote NSW Indigenous students in years three and five, who have made six to 12 month improvements in reading and numeracy, and even bigger gains in writing.

…but the gaps are still not closing fast enough

While these trends offer encouragement in some areas, better Indigenous results do not necessarily mean Indigenous students are closing the gap. For example, the year five reading gap is widening in Queensland, because non-Indigenous students have improved even more since 2010 than Indigenous students have.

The following table shows how the achievement gap has changed since 2010 for each jurisdiction and year level. To be on track to meet the 2018 target, a gap must have shrunk by at least 45% by 2017.

No state is on track to halve the gap by 2018 in any subject or year level

Percentage change in the gap in equivalent year level between Indigenous and non-Indigenous students in each state from 2010 to 2017 (2011 to 2017 for writing). A green cell (with a positive number) indicates that the gap has closed substantially, while an orange or red cell (with a negative number) indicates a gap that is growing. Yellow cells indicate little change in the size of the gap.

There are places where the gap is genuinely closing - for example, numeracy in Tasmania, and year nine reading in Victoria, SA and Tasmania - but they are few and far between. And nowhere is the gap closing fast enough to be on track.

Read more: The gap of Indigenous disadvantage is being closed too slowly: report

What should be done

There is no easy way to improve Indigenous education outcomes at scale. But here are three things that would help.

First, measure and track the learning gaps more accurately. Presenting the gap in years of learning brings home the reality of educational outcomes for too many Indigenous Australians. The national target should reflect this reality, and could easily be changed as part of the current Refresh of the Closing the Gap agenda. Our submission to the Refresh process makes this recommendation, and includes additional analysis not covered here.

Second, systematically evaluate schools where Indigenous outcomes are particularly high, or learning progress particularly strong. Even better, try to understand examples of improvement at scale. For example, researchers should try to identify the causes of the recent gains in very remote NSW schools in year three and five, to see if there are lessons that would apply more broadly.

Third, acknowledge the implications of the current gaps for targeted teaching. Given that so many year seven and nine Indigenous students are working at an early- to mid-primary school level, policymakers need to ensure teachers in remote secondary schools have the training and support to teach basic reading, writing, and numeracy. Few secondary school teachers have these skills - they are trained to teach subjects, not foundational skills meant to be mastered in primary school.