A nationwide strike by secondary school teachers will see hundreds of schools close today.
Almost 18,000 teachers will take to the picket lines calling for equal pay for equal work.
400 schools were closed yesterday for health and safety reasons, as ASTI members withdrew from supervision and substitution duties.
Today's industrial action centers around pay for newly qualified teachers and will see an extra 100 school closures.
Kieran Christie is General Secretary of the ASTI: “We would prefer that we were not where we are. Our members would prefer to be in their classrooms teaching their students.
“Our message is pretty simple: equal pay for equal work.
“We haven’t secured movement from the Government in relation to that matter. This is our second day of strike in relation to it and we need to see movement, we need to see real commitment from the Government to address that matter in a timely fashion."
Minister for Education Richard Bruton says the ongoing dispute is very disappointing: "The issue at the heart of this dispute is a decision by the ASTI that their members would not work the extra hours that every other public servant worked.
"The consequence, if that principal were accepted, are unthinkable for Government, it would as I say represent the withdrawal of the equivalent of 14,000 people from frontline services.
"That would have a devastating impact."