Setting up charter schools in poor, quake-ravaged parts of Christchurch would worsen the huge problems teachers already face, Labour says.
The party's five Christchurch MPs say poor areas targeted for the trial are in the worst-affected quake zones where schools are reeling from roll losses of up to 20 per cent.
"Principals are being forced to issue redundancy notices because of cuts to next year's funding, now they're being told they are failing schools held captive by teachers," they said in a joint statement on Thursday.
"That's offensive to those who teach at a decile 1-4 school... there's a whole array of challenges and staff cuts include counsellors who help pupils address all the complex issues presented by growing up in poverty."
The charter school proposal is part of the support agreement National and ACT signed on Monday.
Poorly performing state schools would be taken over by private business organisations, community or iwi groups and charities.
They would then be run like private schools, outside the rules for state run schools, with boards free to decide teaching practices and pay teachers on a performance basis.
They would still be state funded, with input from the private sector.
The support agreement says the trial should start in south Auckland and disadvantaged parts of Christchurch.
Teacher unions fiercely oppose charter schools and a campaign against them has already started.
Prime Minister John Key is defending them, saying they could bring out excellent leadership and results in areas where children are poorly served by state schools.