The ACT's Aboriginal and Torres Strait Islander students are up to 20 percentage points behind their non-Indigenous counterparts on NAPLAN tests by year 9. The average in metropolitan areas is 10 points.

University of Canberra Indigenous education expert Chris Sarra said this week a concerted effort from the ACT would help close the gap - the equivalent of two years of learning - within years.

Asked by Canberra Liberals leader Alistair Coe why the ACT fared so badly, given it spent the most per capita on its students, education's director-general Natalie Howson said it was a "very good question".

"I can't answer your question authoritatively because there actually isn't any research which is definitive which would give us the answer to your question what is happening and what is the difference between jurisdictions, so we really can only hypothesise," she said.

"Certainly, I would emphasise that the ACT still remains in the top group of performing jurisdictions if you use our standardised means test through NAPLAN as the measure."

Deputy director-general Deb Efthymiades pointed to the ACT's unique housing mix as a potential factor, and Education Minister Yvette Berry noted that Professor Sarra was working with the directorate on its inequity-focused Future of Education project.

Mr Coe pushed for firmer research into the issue.

"A body of work seems to be required in this space - I'm not talking about opinion, albeit expert opinion," he said.

"I'm talking about actual academic rigour to determine how do you deal with deeper issues."

Ms Berry responded: "We recognise it's not always going to be a solution that a clever academic comes up with that's going to work with our community here in the ACT and that's why the conversation with them about coming up with a solution that works for those communities and for all those different families that is student-centred and that we can support parents as well in that conversation … to make sure that we get the best possible academics."

The Education Directorate has come under fire in recent months for poor results among public school students when contrasted with comparable jurisdictions interstate.

In an Auditor-General report released in May, a comparison of public schools' 2015 NAPLAN results with similar schools elsewhere found the majority of ACT government schools' results were lower than those with a comparable level of socio-educational disadvantage.

Education academic Stephen Lamb, who authored a separate report on the issue and was quoted extensively in the Auditor-General report, said a divide between the rich and poor in public schools contributed to the ACT's poor showing.