Delegates and guests attending the school managers' conference last night said the ASTI now faced tough decisions on future industrial action.
The general secretary of the Joint Managerial Body (JMB), Mr George O'Callaghan, said the ASTI should reconsider future industrial action in the light of the tight vote.
"It is a disappointing result from the point of view of ensuring industrial peace in schools. We hope any future disruption will not be too acute," he said. It would be difficult for ASTI to stage further industrial action knowing that half of its members supported the Labour Court package.
The narrowness of the vote placed a question mark over any future industrial action by the ASTI, said Mr Michael Moriarty, general secretary of the Irish Vocational Education Association. There were now questions about the "moral validity" of further industrial action.
"The ASTI standing committee seems to have misread and misjudged the mood of the membership," he said. Referring to the rejection of further exam disruption, he said: "I'm not surprised. The idea of hitting exams was misguided and ill advised. It did damage to the natural allies of teachers," he said.
Ms Barbara Johnston, public relations officer of the National Parents' Council (post-primary), said the result was not good for the ASTI.
"It means the union is split on the way forward. From a parent's point of view I would like to see them develop a strategy which would unite their members," she said. "They have mishandled the whole dispute. They did not go back to their grassroots often enough."