"Many people, before they had this information, would have said to themselves private equals good, and public equals bad," Ms Gillard told an audience at an education conference in Dubai on Saturday.

"And then when we actually had the data set, what people worked out was a lot of state schools were outperforming expectations, going really well; and a lot of non-government schools - some of which parents were paying very high fees for - weren't going as well as their historic reputation would have led people to believe."

She did not name names. But changing enrolment patterns support her view.

The 40-year shift towards private schooling has reversed, with the latest ABS figures showing public schools have increased their share of enrolments from a historical low of 65.1 per cent in 2014 for two consecutive years to 65.5 per cent.

In 1977, 79 per cent of students nationally went to government schools.

Ms Gillard also defended NAPLAN, one of her major reforms as education minister, which she called "a huge transparency project", noting there was opposition from the teachers unions against its introduction.

"Parents in countries like Australia make choices all the time about what school to send their children to," she said, noting that she was herself a product of a state school.

"Whether they get that information from people who they run into at the shops, out of a tabloid newspaper, or they use the rich and transparent data set on the MySchool website, they will make those choices. My own view is that choices about education are better if you have the information.

"It is good contextual information, it can't be used as league tables. What it can be used for is it compare schools with 60 other schools teaching children at the same levels of educational advantage and that's very profound information to know."

Ms Gillard has kept a low profile since exiting politics in 2013, save publishing her 2014 memoir My Story.

She is the Chair of the Global Partnership for Education, a fund that works to get more children in the poorest nations into basic schooling. She has a couple of visiting fellowships in the field.

It was in her capacity as a global education advocate that Ms Gillard appeared at the Global Skills and Education Forum, a conference funded by an Indian billionaire and education philanthropist that pitches itself as "the Davos of Education".

She gave a sunny account of her introduction of "Gonski" funding ("a profoundly new way to think about things"), and would not comment on the perilous future of needs-based funding under the Turnbull government in the absence of a new COAG agreement.

She also would not be drawn on criticism that NAPLAN was being used for purposes beyond its original design, such as the controversial use of year 9 NAPLAN results as a literacy and numeracy prerequisite for the Higher School Certificate in NSW.

"I don't as you know try to get involved in debates in Australia, but trust the only Australian journalist in the room to try."