The INTO has stepped up its campaign on overcrowded classrooms by launching a nationwide petition of parents.
In a move timed to maximise pressure on the Government in the run-up to the next election, the union is asking parents in over 3,000 primary schools to back a petition demanding smaller class sizes.
The petition will be forwarded to Minister for Education Mary Hanafin. Parents are being asked to sign a letter, addressed to Ms Hanafin, calling on the Government to implement its promises to reduce class sizes in primary schools. The INTO says class sizes in the Republic are the second highest in the EU.
Class size is a sensitive issue for the Government. Its Programme for Government promised to reduce average class sizes to 20 and under by next year for all pupils under nine. But this commitment has been abandoned.
In its letter to parents, the INTO says the petition is "the start of a campaign that will last right up to the next election if promises made are not kept.
"If necessary, the INTO is determined to ensure that class size will be high on the political agenda. Promises made before and after the last election must be honoured."
General secretary John Carr said: "After four years of this Government we still have teachers being appointed to schools on the basis of approximately one teacher for every 29 children."
Last night Ms Hanafin said she was "disappointed that the INTO are resorting to engaging children in what is essentially a political lobbying campaign, particularly as parents all over the country will know that class size has been reduced considerably with additional teachers targeted at children with special needs, from disadvantaged areas and those with English language needs."
She added: "By next September there will be no less than 4,000 extra teachers in our primary schools, compared with 2002."