The Australian Education Union and ACT Council of Parents and Citizens Associations said the trial had been enormously unpopular among school communities and the government should abandon it.

The ACT Education Directorate has confirmed it has reduced from 23 to eight the number of schools trialling an ''average cost budget model'', which requires them to use a single budget allocation to pay for their staff salaries, rather than being allocated the individual staff they need by the directorate.

The 18-month trial began in 2011 with six schools, before increasing to 23 schools last year.

ACT director-general of education Diane Joseph met with school principals on Tuesday to discuss the ACT's planned ''response to the empowerment measures in light of signing up to the Gonski reforms''.

She said the trial had been ''scaled back to eight over the past few months because the landscape has fundamentally changed under the Gonski reforms, which require greater accountability around student resourcing. We need our trial to allow us to be more focused and work more intensively with the chosen schools to inform how the ACT responds to the national reforms.''

Both the union and council have lobbied vigorously against the financial autonomy model, which forms part of broader school autonomy moves across the ACT and other states.

They warn that a consequence of the budget autonomy could be mounting pressure on principals to hire cheaper, less-experienced teachers and cut back on specialist positions such as teacher librarians or English as second language specialists.

There is also concern that class sizes may increase in an attempt to reduce staffing costs.

Australian Education Union ACT secretary Glenn Fowler said there was mounting evidence - most recently in two reports from the Grattan Institute and Melbourne Graduate School of Education - questioning whether increased autonomy improved school outcomes.

''The ACT's school autonomy trial has seen very real problems and our principals and teachers have been expressing their concerns. The ACT's Gonski sign-up, whilst very welcome and essential, has added an extra layer of complexity to the picture of school funding,'' Mr Fowler said.

He welcomed the trial number being scaled back but said ultimately the policy was flawed and should be abandoned.

ACT P&C Council president Vivienne Pearce said parents had been very concerned about the trial and there was no convincing argument ACT schools would be improved by the policy.

''We have always been concerned about the financial aspects of school autonomy,'' Ms Pearce said.

Ms Joseph said the directorate had asked the 23 schools involved whether they wished to drop out, but only one or two requested this.

She said the wider school empowerment agenda had been

said the wider school empowerment agenda had been well received by school leaders.

The directorate had chosen to continue the trial with Dickson College, Hawker College, Weetangera Primary, Canberra High, Telopea Park School, Canberra College, Malkara Specialist School and the Namadgi School.

''We looked at the expertise and capacity of schools and picked a number that was manageable.'' She noted ACT schools were already operating with a large degree of autonomy following three decades of School Based Management.

The smaller trial of financial autonomy would now consider ''how we account for resources that go to our schools and show the impact they have on improving student outcomes…We need to come up with some intensive analysis and design and then stress-test any recommendations.'' She believed the trial would continue over the next year with the ACT having signed up to a six-year national reform program under Gonski.

According to a survey conducted last year by the AEU on how the autonomy measures were affecting schools, 70 per cent of the 33 principals and deputy principals who responded anonymously said the impact was negative.

They also overwhelmingly experienced higher administrative workloads during the trial, warning they were being distracted from the task of school leadership while they concentrated on accounting issues.