Around 3,000 classroom assistants in Northern Ireland, who are members of the public service union NIPSA, have begun an indefinite strike.
Three other unions are consulting members on an offer of a one-off £15million payment to compensate for a change in the way salaries are calculated.
They said that could mean £2,500 for each assistant. But NIPSA insists that the offer does not go far enough.
NIPSA members went on strike for three days last week and one day the previous week. There have been negotiations between employers and the four unions concerned but NIPSA members have turned down the latest proposals.
The union says the latest industrial action will continue until employers table a pay offer which addresses three key issues.
These include basing the assistants' pay on a working week of 32.5 hours rather than 36 hours and continuing to be paid the special needs allowance of £1,107 per year or 65p per hour.
NIPSA General Secretary John Corey said the classroom assistants were absolutely justified in taking strike action, which is their fundamental right.
He said the sooner the education boards and education department started talking seriously to the union about the dispute, the sooner schools could get back to normal.
The Education Minister Caitriona Ruane has been urged by the Assembly's Education Committee to use her influence to end the dispute.
