The INTO has criticised the Department of Education for not sufficiently supporting pupils in disadvantaged areas.
Primary school teachers feel a review of the Delivering Equality of Opportunity in Schools (DEIS) scheme has not made enough progress.
Teachers condemned class sizes remaining unchanged in disadvantaged schools despite minor reductions in schools outside of DEIS areas.
Shane Loftus, who is part of the INTO's Central Executive Committee, says action must be taken.
"In the last two years, there has been very little engagement with that group," he said.
"The refusal of the Department to meet and to come up with the solutions we need for DEIS at the moment means that the children who need that support are left without it.
"They don't get a second chance. They don't get to be in primary school for the length of time this review group is taking."