Unions criticising a new funding proposal as "bulk funding" shows they don't trust principals and boards, Education Minister Hekia Parata says.
School classes will be disrupted in September as 60,000 union members hold meetings about the potential changes to school funding.
Each school will decide how to deal with the disruption but it is likely some will close when the meetings take place.
Parata said the meetings and comments from union leaders today, "basically represents that the unions don't trust principals".
Claims the proposals would lead to class sizes were wrong, Parata said.
"I don't agree with that at all and I'm really disappointed that there is so much distrust of principals.
"We are trying to create greater flexibility in the system that gives the principal and board on the spot the flexibility to say, 'What do we need to cause learning to happen for these kids'."
The two main education unions have taken the unprecedented step of calling the meetings together in the hope of pressuring the Government to drop the proposed changes.
Speaking at Wellington Girls' College today, New Zealand Educational Institute (NZEI) president Louise Green said 50 meetings would be held across the country from September 5 to September 16.
"We don't want to see any quality teaching traded off for other resources...when teachers are traded off then class sizes will go up, curriculum choices can be restricted, there could be non-qualified teachers employed because they are cheaper.
"The changes proposed are really significant. We have gone from talking about a decile funding review to a total overhaul of the way funding and staffing is delivered to schools."
Consultation documents published by the Government in June included giving schools a bulk allocation of funding - called a "global budget".
That funding would include cash instalments for school expenses and a credit system for salaries.
Principals would determine the split between cash and credit, with the flexibility to make adjustments during the year.
Un-spent credit would be paid out at the end of the year.
The Ministry of Education says the global budget system would not be the same as the controversial bulk funding of teacher salaries that caused widespread protest and was ditched in 2000.
That was because schools would not be charged teacher salaries - the schools would receive credits for their teachers, not funding to pay them.
Bulk funding was introduced on a voluntary basis in the 1990s and schools that opted-in were given money linked to their allocation of teachers. They could then spend the money as they wished.
Labour's education spokesman Chris Hipkins said the global budget proposal was bulk funding, and would result in bigger class sizes and reduced range of subject choices.
"This is Hekia Parata's second attempt to drive through a policy of larger class sizes. She was forced into an embarrassing back-down in 2012 after parents voiced their outrage."
Angela Roberts, president of the Post Primary Teachers' Association (PPTA), said Prime Minister John Key had said the funding proposals wouldn't go ahead if the education sector didn't want them.
That message would now be given loud and clear, she said.
"We are trying to make sure that Cabinet hear loudly and clearly what we know needs to happen and that this goes."
The school funding documents are part of the Government's Education Funding Review, which has also proposed scrapping the decile system and targeting funding to children deemed at risk.
When the Herald revealed the at risk funding proposal in March, Key was asked about it and said he had been briefed by Education Minister Hekia Parata on school funding, and discussions about what could replace the decile system.
"One of the things they said to me was they wouldn't really be progressing the issue unless they could get the other stakeholders on board - the unions and others," he said at the time.