Proposed changes in the way schools are run could cost taxpayers up to an extra $2 billion a year, some principals say.
The Waitākere Area Principals' Association says the high cost means that many of the ideas proposed by a taskforce led by former principal Bali Haque "are simply not going to fly".
Submissions from other principals' groups also strongly oppose the taskforce's central proposal to transfer all the legal powers of boards of trustees to about 20 new regional "hubs".
The NZ Principals' Federation says in its submission that the hubs "evoke images of 'bureaucratically bloated' Regional Education Boards, a long-rejected entity which represented powerful central control".
The regional boards were abolished when all schools became self-governing in the 1989 reforms known as "Tomorrow's Schools".
The Haque taskforce has proposed re-creating 20 "hubs" to employ all principals and teachers so that they can be moved to where they are most needed, as a way of reducing destructive competition between schools.
It has not provided any costings of its proposals and Haque said it did not plan to do any before giving its final report to Education Minister Chris Hipkins by June 30.
However the Ministry of Education and possibly the Treasury are expected to provide costings before the Government makes decisions on the final report.
Hipkins has told colleagues that his report-back will include "the relative costs and benefits of the proposals that the Minister intends to progress" and "the estimated fiscal costs and regulatory impacts of those proposals".
Laingholm School principal Martyn Weatherill, who wrote the submission for the 100-strong Waitākere principals' association, said proposals for a learning support co-ordinator in every school, and to boost primary schools' management staffing to the same level as secondary schools, would add about $414 million a year for about 4500 extra teachers.
He said another proposal to double "equity funding" for disadvantaged students from 3 per cent of operational funding to 6 per cent of operational and staff funding would cost a further $290m a year.
"These three recommendations total over $700m per annum operations and $180m in capital costs," the submission says. "All of this before we contemplate the costs of creating and staffing the proposed education hubs."
Weatherill said the proposal for about 20 hubs meant they would be about the same size as the 20 district health boards, but he said: "That is saying to a principal at Invercargill, you are going to be a principal of a school in Dunedin. At that point the principals and their families hit the roof."
He said Haque had told public meetings that his final report might propose more, smaller hubs. But Weatherill said more hubs would be even more costly.
"While we see significant benefits in a number of the recommendations contained in the report, we have conservatively estimated the key recommendations at an implementation cost of between $2b and $4b and a running cost approaching an additional $2b per annum," the submission says.
"As school leaders we have been told that there is simply no more money for education.
"We hope that, as a taskforce, you are privy to information that we are not, otherwise many of the great recommendations in this report are not going to fly."
Haque said his taskforce was now considering more than 1200 written submissions and 3300 responses to an online survey which asked for the public's views on each of the taskforce's 31 recommendations.
He said costings were "a very, very complex business" and were not part of the task force's terms of reference.
But he added: "We are quite clear that we think this is a phased process."