Two of the four options for families in Bungendore, Googong and other areas near the ACT face the greatest socioeconomic disadvantage in Canberra, based on factors such as parents' income and education.

The government's new policy, which began this year, stops NSW students from attending inner-north and inner-south schools.

Instead, if they want to attend a Canberra school rather than one in NSW, they must attend one of four primaries in Tuggeranong for families from Bungendore, Braidwood and other areas to the south and east; and one of three primaries in Belconnen for families from Yass, Goulburn and other areas to the west and north.

It is a big change for NSW families who for many years sent their children to schools such as Campbell.

For parents south and east of Canberra, the four primaries they can access are Gilmore, Richardson, Calwell and Wanniassa. All rank in the bottom 12 of Canberra's 56 public primary schools on socioeconomic indicators. Three rank below the national average.

Gilmore has a socioeconomic advantage score of 899, against a national average of 1000 and a Canberra primary-school average of 1088, according to NAPLAN data released last week. Sixty per cent of Gilmore's students are in the bottom quartile for disadvantage. Just 4 per cent are in the top quarter.

The picture is reversed at Campbell primary, where 65 per cent of children are in the top quarter of the population on socioeconomic advantage, and just 2 per cent in the bottom quarter.

It is rosier for the Belconnen schools to which families from Yass, Goulburn and areas north and west of the ACT are directed: Charnwood-Dunlop, Evatt and Florey. All rank above the national average, although they are still in the bottom half of Canberra's schools.

At Charnwood-Dunlop, 17 per cent of students are in the top socioeconomic quartile and 27 per cent are in the bottom, close to a national average. At Florey, which the most advantaged of the primary schools for NSW families, 31 per cent of students are in the top quartile and 17 per cent in the bottom.

But Florey, like many of Canberra's schools, does worse than most schools in its socioeconomic cohort in national literacy and numeracy testing. When compared with 56 schools around the country with similar levels of advantage, Florey's year 5 students in 2017 ranked in the bottom 10 in all five subjects areas tested. The comparison includes private schools.

The story is by no means confined to Florey. At Campbell, now barred to NSW students, the NAPLAN performance in year 5 in 2017 was similarly poor when compared with other Australian schools with the same socioeconomic profile.

Campbell's socioeconomic score is 1143, one of the most advantaged schools in the ACT. But when compared with about 60 schools with students from similar backgrounds, Campbell's NAPLAN performance is also relatively poor; its year 5 students ranked between 48th and 58th place in the five subjects (reading, writing, maths, spelling and grammar).

Wanniassa's year 5 students buck the trend, performing well compared with children in other, similar schools. Wanniassa's year 5 students came seventh and eight for writing and reading last year compared with about 40 similar schools (and between 18th and 24th for the other subjects).

The ACT Education Directorate denied it was sending NSW students to the most disadvantaged schools. A spokeswoman pointed out that all the northside schools open to NSW children had a socioeconomic score above the national average.

The northside schools were "more advantaged than the equivalent schools in the surrounding region" and the southside schools were similar, she said.

In fact, Gilmore is more disadvantaged than any of the four government primary schools in Queanbeyan, the two in Cooma and the primary schools in Braidwood and Bungendore. And of those, only Queanbeyan South has a lower socioeconomic score than a second of the southside schools, Richardson.

Overall, though, the NSW schools are more disadvantaged than most ACT schools.

The Belconnen schools for parents north and west of Canberra are largely higher on the socioeconomic scale than the local NSW schools, especially the Goulburn schools.

The spokeswoman said every ACT child was guaranteed a place in their local school but enrolments had been growing at the fastest rate in Australia, making it impossible to enrol out-of-area students.

"The procedural change for NSW enrolments simply reflects this reality," she said. "Importantly, it also provides NSW students with enrolment certainty because they will now be guaranteed a place in an ACT public school."

NSW students received the same opportunities as ACT students, including the Chromebooks recently handed out.

Asked about schools' generally poor performance, the spokeswoman said "great teaching and learning occurs in all ACT public schools" and NAPLAN scores were a poor tool to assess school performance.

She pointed to Charnwood-Dunlop's program to link parents, teachers and students in reading intervention, which brings the community together and has life-long benefits not necessarily reflected in NAPLAN scores.