Secondary teachers say schools could face closure in the autumn if the Government does not engage with them over pay.
The ASTI executive has staged a demo outside the Dáil in the long-running dispute over pay restoration and the rates that newly qualified teachers are paid.
The union has refused to accept the Lansdowne Road pay agreement which came into effect today.
President elect of the ASTI Ed Byrne rejected the idea that the deal is the only way the Government will negotiate.
"The truth is if you really want to, you can negotiate," he said. "The only law (governing this) is emergency law and the Minister for Finance says the emergency is over, so I don’t see why we would be subjected to emergency law any longer."
From today ASTI secondary school teachers and members of the GRA may face significant pay freezes.
The penalties, which include the freezing of increments and the non-payment of supervision fees, can be imposed under legislation known as FEMPI.
As a result, ASTI members will protest outside the Dáil calling for the Government to honour the terms of the Haddington Road Agreement, which expires today.
However, the Government has said the Lansdowne Road Agreement is the only mechanism for pay restoration, a deal the members will not sign up to.
Kieran Christie ASTI General Secretary has described the end of the Haddington Road Agreement as a “tough day” for his union’s members.
“Today is a very tough day for ASTI members,” said Christie.
“Even though they have adhered to all the terms of the Haddington Road Agreement - and they are not part of the Lansdowne Road Agreement - this legislation is being used very punitively against them to attack their terms and conditions of employment, and that’s entirely unacceptable.”