Around 550 learning support specialists will go on strike on Tuesday in protest over their workloads and pay.
Learning support specialists including psychologists, speech language therapists, early intervention teachers and occupational therapists, employed by the Ministry of Education, will walk off the job for a full day on August 21.
They say they're "insulted" by the latest offer from the Ministry of Education of a pay rise of 2 percent on ratification and a further 2 percent by March 2019.
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NZEI Te Riu Roa executive member Byron Sanders told Newshub the situation has reached crisis point for its members.
"We're not able to recruit and retain specialists into these roles because the remuneration packages are not good enough and quite frankly the workloads are absolutely dire."
Mr Sanders said vacancies across the country weren't being filled, putting extra pressure on existing learning support workers to meet the needs of children.
He said he knew of learning support specialists who had caseloads of over 100, and psychologists with caseloads of more than 30 children.
"If you're expected to work with the most vulnerable, risky children in our school settings you can't be working with case loads of over 30. You need to be in there providing really, really intensive support to ensure there are lots of plans around those children."
He said NZEI Te Riu Roa is willing to continue to negotiate with the Government.
"We're willing to negotiate, we're willing to have things go both ways but what we're saying right now is a 2 percent pay rise is not good enough and no work going into ensuring that we have manageable workloads is not good enough."
Fairhaven School principal Paul Hunt said: "I don't think people realise the extent to which schools are coping with additional learning needs and additional behaviour needs."
Mr Hunt said at his school in Te Puke a number of children had severe behavioural needs which could result in them swearing at teachers or students, destroying items, or running away and not doing what they'd been told to do.
"We love the children being in our school it's just the fact that we need the extra support to be able to cater for them so they have the best learning experiences that they can in our school. We can't do that without the extra support from learning support."
Mr Hunt said learning support specialists had been underfunded, under supported and underappreciated by successive governments.
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In a statement to Newshub, Education Minister Chris Hipkins said the Government understood the concerns of the Ministry's field staff and was actively working to address them.
"We are making good progress but we can't do it all at once. I encourage the Ministry and NZEI to continue negotiating. We can't fix nine years of neglect in one go," he said.
"This year's Budget had the biggest increase to learning support funding. We have already provided additional funding for and the ministry is in the process of recruiting 52 extra specialists to expand the severe behaviour service, 28 extra specialists to help reduce waiting lists for early intervention services, plus 15 extra specialists for ORS (Ongoing Resourcing Scheme), and six specialists for the Intensive Wraparound Service."
Earlier this week the ministry signed a pay equity settlement with around 329 early childhood and primary education support workers, which will see pay increases of up to 30 percent.