The Department of Education has revised the designation of a number of schools that were awarded DEIS or disadvantaged status several weeks ago.
An additional 79 schools were granted DEIS status in February, in two different categories - urban and rural. The urban designation attracts the most additional funding.
However following queries from RTÉ News, the Department has changed the categorisation of a number of schools on its new DEIS list.
It has told RTÉ News that it has now changed the methodology it is using and will now write to schools requesting the eircodes of pupils so that it can further refine its assessment of their economic backgrounds.
The Department of Education has said that the new model for identifying schools eligible for additional supports under its DEIS programme is a significant improvement on the previous system.
In a statement this evening, it reiterated that the latest list of schools to be included in the programme is a first step.
It said while some schools had expressed disappointment at not being included in DEIS on this occasion, none of those schools had higher levels of disadvantage than the 79 that were recently added to the scheme.
It said classification of primary schools as either urban or rural related to resource allocation and not to eligibility for DEIS.
It said consultation with education stakeholders had shown a clear desire for a more responsive and tailored methodology.
Initially the department defended its placing of some schools in the urban DEIS category, even though these schools had profiles that looked distinctly rural.
In the case of one rural school whose categorisation as urban was queried by RTÉ, the Department at first said that pupils attending the school were from urban homes.
However, earlier this week the Department acknowledged errors on its part. Two schools, including the rural school referred to above, have been recategorised from urban to rural DEIS status.
Two other schools have been recategorised as urban.
This mistake is likely to exacerbate concerns expressed by a significant number of schools as to the reliability of the Department's new system for measuring disadvantage.
The Department said it is now changing one measure used in its new system, and seeking pupil eircodes in order to make its assessments more accurate.
It said it hopes to "run the whole process again" in July when it has up-to-date data on pupils from schools, as well as new census data.
The two schools removed from the urban category, which attracts more funding, are Fairgreen National School in Belturbet, Co Cavan, and Scoil Naomh Iosaf, which is in Co Donegal.
Fairgreen National School is a small Church of Ireland school with 37 pupils. Belturbet is not classified as an urban area.
Scoil Naomh Iosaf, near Ballymagann in Donegal, has 56 pupils and is surrounded by farmland and hills. Its principal describes it as "a small country school" and confirmed the pupils all have rural backgrounds.
Two Mountrath schools were informed on Wednesday that they will be recategorised as urban DEIS schools.
The Department of Education said it was using the electoral district the pupil came from to assess levels of disadvantage and urban or rural status.
It said it will now use settlement areas which is a smaller more precise measure.
The schools have been informed of the mistake by phone but have yet to receive written confirmation of their recategorisation.
Louise Tobin, who is principal at St Joseph's Primary School in Tipperary Town, has questioned the reliability of the Department of Education's new system for measuring disadvantaged schools.
Speaking on RTÉ’s Drivetime, she said her school serves a disadvantaged community and was confident it would feature on the urban DEIS list but it was not.
She said the Department told her geocodes were used, but when she questioned this, she was asked by the Department for the eircodes of her pupils.
"Surely, the department, no more than anybody else in the public sector, is working at planning properly, delivering properly and not making mistakes. I mean, we are talking about the lives of all of the little children in Tipperary town, coming from disadvantaged homes who deserve a better chance; who deserve DEIS, delivering equality in schools," said Ms Tobin.
Schools are not obliged to supply pupil eircodes to the Department. However many schools who feel they should have access to the supports that come with DEIS are likely to be keen to send the codes to the Department.
Fianna Fáil has called for an independent review mechanism for DEIS appeals.
In a statement the party's Education Spokesperson Thomas Byrne said confirmation that serious errors had been made in determining access to the DEIS scheme showed that an appeals mechanism was urgently needed.