Ulster's special schools were last night waiting to see if they face further closures after talks between unions and management failed.
The four trade unions involved in the classroom assistant dispute failed to reach agreement with the Education and Library Boards after two weeks of intensive talks involving the Labour Relations' Agency.
Management last night appealed to public service union Nipsa to ensure that no special schools will be affected by any further strikes.
Members of Nipsa have already spent 10 days in total on strike.
However, Nipsa said it will hold meetings with members on Thursday to discuss its course of action.
It had been hoped that, following intervention by the LRA, that a deal could be brokered.
The development was hailed a positive step for schoolchildren caught up in the industrial action.
Up to 3,000 Nipsa members began strike action at the end of September for the retention of the 32.5 hour week, special needs allowance and recognition of NVQ Level 3.
Meanwhile, the three other main unions involved in the negotiations are due to ballot members on the existing deal.
A spokesman for the Education and Library Boards last night said: "The employers are frustrated and angry that the fourth union involved, Nipsa, is still refusing to ballot its members on this offer and at the same time is unable to provide the employers with realistic alternatives to the offer which they say is so unacceptable.
"The employers entered the two weeks of talks in good faith and firmly believe they have engaged as fully as possible in a serious effort to explore all aspects of the current offer.
"The employers were keen to maximise the available resources for the benefit of classroom assistants and are extremely disappointed that Nipsa is unable to respond positively and has completely isolated itself," he said.
"At the last stage of the talks, when it was absolutely clear that no agreement with Nipsa could be reached, the employers called on them to ensure that no special needs child in Northern Ireland will be denied access to their education because of strike action.
"The employers call on NICICTU and every responsible trade union to support this plea to protect our most vulnerable children."