Some fee-paying second-level schools have received grants of over €1 million each from the State for building and other projects since 1995, according to new figures.
The schools include several which charge day students over €3,000 a year in fees and boarders about €10,000 a year.
This support from the State is in addition to over €70 million annually which the fee-paying schools receive to subsidise teachers' salaries and allowances in their schools.
The fee-paying schools that received over €1 million each in State support for buildings include Kilkenny College (€2.6 million), Loreto Beaufort, Rathfarnham, Dublin (€1.6 million) and Belvedere College, Dublin (€1.1 million).
The Teachers' Union of Ireland (TUI) has expressed dismay at the level of support.
Its education officer, John MacGabhann, said taxpayers' money is "being provided to schools which already enjoy significant advantages and generate income from their fees".
The reality, he said, was that many schools in the State sector were extremely poorly equipped. But these schools were open to all students and not just reserved for those who can afford fees, he said.
The TUI would be happy for fee-paying schools to receive such funding if they allowed all students to enter their schools, as was the case in the free school sector.
"If these schools didn't charge fees and ran on the same basis as others, they would be available to all," he said.
Other schools which have received considerable support include Sligo Grammar and High School (€2.07 million); St Killian's German School, Dublin (€1.4 million); and The High School in Rathgar, Dublin (€958,000).
Others which feature prominently include Dominican College, Newbridge, Co Kildare (€725,000); and St Joseph of Cluny in Killiney, Dublin (€713,000). Some of the schools in question have launched significant fundraising campaigns among parents and alumni to allow for extensive building and modernisation works in recent years.
But the figures also indicate that other well-known schools - such as Blackrock College,Dublin; Gonzaga College, Dublin; and Clongowes Wood College in Co Kildare - have not received any State support for major building works since 1995.
The figures relate to the period between 1995 and 2004. In total, fee-paying schools received over €16.5 million in State support for building projects during this time. This compares to a total capital works allocation for second-level schools in the State sector of €187 million last year, although some of this funding was not spent.
The new figures will revive the controversy over State support for the 58 fee-paying schools in the State. The former education minister, Noel Dempsey, was uneasy about taxpayer support for these schools. But the current Minister, Mary Hanafin, has said she has no plans to review funding for such schools.
In an Irish Times interview earlier this year she said; " All we really do for the fee-paying schools is to pay the teachers. We don't give them capitation or related grants. We support only a portion of their capital costs for their building projects.
"The reality is that we would still have to pay teachers if all the pupils moved out of fee-paying schools and into the State sector in the morning. I have no objection in principle to paying teachers in fee-paying schools."
The State subsidises fee-paying schools by paying their 1,600 teachers, at an estimated cost of some €70 million. About 20 of the 58 fee-paying schools are Protestant, most of the others are Catholic.
The State does not provide any support to the booming grind school sector, which pays its own teachers' salaries.