The warning was made last week by Fern Turner, NAHT regional officer, after the Northern Ireland education minister, Barry Gardiner, met leaders of the four teachers' unions involved in the strike, which began at the start of January and is now into its fifth month.
Ms Turner said, 'Things are not good at all. Education is being disrupted.
Teachers had said that it wouldn't affect children, but it has.
'Teachers are not covering for absent colleagues, so substitute teachers have to be brought in on each and every occasion. This has created a financial burden on schools and the result will be redundancies that would not have been necessary. It is extremely worrying.'
The strike has affected every school in Northern Ireland, with teachers carrying out only their core duties and refusing to cover for colleagues.
Mrs Turner said it had made an 'impact in the nursery sector, where teachers are no longer doing the planning, preparation and assessment that they usually would'.
She was critical of teachers who 'seem to prefer to live with this situation' and are 'happy to leave the school at 3.30pm and attend no staff meetings'.
The teachers are striking for extra pay that would bring them up to the same level as their colleagues in England and Wales. But Mr Gardiner told the unions that in order to qualify for more money they would have to 'accept the link between extra pay and performance management', as has been the case in England and Wales since 2000.
He said, 'I do not believe that good teachers in Northern Ireland have anything to fear from performance management or would see it as a threat.'
