Over 37 per cent of primary school pupils in north Dublin are being taught in classes of 30 or more, according to the INTO. The union claims class sizes in many areas are increasing, despite Government commitments to a class size of 20 pupils and under for all under-nines by 2007.
In its pre-budget submission the union says 34 per cent of pupils in "the Minister's own constituency" of Dún Laoghaire-Rathdown are in classes of over 30. The pattern is broadly similar, it says, in Kildare and Meath.
The Republic has the second most crowded classrooms in Europe, according to the union's general secretary, John Carr. He also points out that the State is one of "the lowest spenders in the EU on education. If we don't invest more on schooling we are going to be left behind," he says.
The INTO submission says primary education has been "neglected in terms of educational spending.
"Any comparison of primary, second and third level will bear this out.
"Now, at the very time that primary schools are being asked to innovate and change, they are strapped of the necessary funding and staffing levels. If we want a 21st century education system then we must have 21st century, not 19th century, investment."
To support modernisation of the primary education sector the INTO is seeking a range of improvements, including:
Class size reductions in line with commitments given in the Programme for Government.
The ending, over two budgets, of the disparity between primary and second-level funding.
The provision of adequate levels of caretaker and secretarial services in all primary schools.
The development of a catering service to provide hot meals for children attending schools designated as disadvantaged.
The provision of a comprehensive nationwide early education structure and the expansion of existing State-funded early education places.
The immediate commencement of building/refurbishment work in all schools with substandard accommodation.
The INTO says spending on education has increased by just 40 per cent since 1995 - even though "Ireland's wealth has nearly doubled" since then.
It says the Government is spending a far smaller proportion on education than in 1995.