The latest census of ACT schools reveals public school enrolments are in decline, while independent schools are thriving.

Spokesman for the Save Our Schools lobby group Trevor Cobbold said the drift to private schools was a "major concern to us as a society" because it was segregating the community along socioeconomic lines.

Some 42 per cent of ACT students now attend a private school, the highest proportion in the country.

The schools census, issued during the week, is a snapshot of enrolments in every ACT school on February 20 this year. Enrolments in non-Catholic independent schools rose 4 per cent in the last year, on top of steady increases since 2004. In contrast, enrolments in the public sector have dropped every year for the past four years. The Catholic sector is holding steady.

The biggest private schools are Daramalan College, Marist College, MacKillop Catholic College, and St Clare's College.

Mr Cobbold said there was an increasing tendency for middle- and high-income earners to choose private education as a way of separating themselves from people from other backgrounds.

Parents were seeking "secure havens" for their children, undermining Canberra's social diversity and reinforcing prejudice, he said.

Parents were being conned into going private despite evidence that educational outcomes in the ACT were "not much different" to the public system.

Mr Cobbold said the ACT Government's school closures seemed to have accelerated the drift to the private sector. He called on the Government to spend more on teachers, mentors and counsellors to turn the tide.

"We just have to put more funding in, more recurrent funding."

The drift towards private schools had been particularly acute in ACT colleges, where the proportion of students in private schools had risen from 30 per cent to 38 per cent since 2000, he said.

The Government has committed $350 million to overhauling the public system, largely for school upgrades and new schools.

Education Minister Andrew Barr defended the Government's record on public education and said he was reforming the sector to make it more attractive.

He said part of the reason public enrolments had declined was that private schools were now offering classes for more age groups. Very few of the students whose schools were closed by the Government had moved to the private system, he said.

Mr Barr said the Government had recognised more children were being sent to private schools back in 2006 and responded by committing the $350 million for building new schools, upgrading old ones, professional development for teachers, and early childhood programs.

He said Mr Cobbold might dismiss the "bricks and mortar" investment, but parents valued good facilities.