Known data issues
Gaps and problems in the Department of Education's source files, and how this site handles each one.
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1983/84 primary schools workbook is incomplete
The 1983/84 workbook is missing several county sheets, which creates an artificial dip in national and county trend charts.
- What it affects
- National totals, county totals, school counts, and average pupils per school are understated for 1983/84.
- How this site handles it
- Exclude 1983/84 from trend visualizations.
- Scope
- National, county and school figures
- Source notes
- The workbook readme mentions Carlow as missing, but inspection of the workbook shows additional missing county sheets.
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No source workbooks for 1984/85 through 1992/93
The downloaded gov.ie historical source set does not include primary school enrolment workbooks for these years.
- What it affects
- Trend charts have a gap between 1983/84 and 1993/94.
- How this site handles it
- Document the source gap; no chart exclusion is needed because the years are absent.
- Scope
- National, county and school figures
- Source notes
- The gov.ie 1974-2019 section jumps from 1983/84 to 1993/94.
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1974/75 workbook is missing five counties
The 1974/75 workbook has no schools for Cavan, Clare, Cork or Galway, and only 2 schools for Carlow, so national and county totals for that year are far too low.
- What it affects
- National and county totals, school counts, and average pupils per school are understated for 1974/75.
- How this site handles it
- Exclude 1974/75 from national, county and Irish-medium group trend charts. School pages still show 1974/75 for schools that appear in the workbook.
- Scope
- National and county figures
- Source notes
- The 1974/75 workbook lists 2,583 schools, against 3,029 in 1975/76.
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Closed schools' counties are recorded inconsistently
Older workbooks record the county of schools that have since closed in many forms, such as 'Dublin City', 'Cork Co', 'Chorcaí', 'TIPPERARY N.R.' or 'do' (ditto).
- What it affects
- Without matching, county trends would leave out schools that have since closed, and county totals would not add up to the national total.
- How this site handles it
- Match each closed school to one of the 26 counties from its recorded county, falling back to the county in its address. Records that still cannot be matched count nationally but not in any county.
- Scope
- County figures
- Source notes
- School lists, planning areas, patrons and local authorities on county pages still show only schools in the latest year's figures. Planning-area trends only include schools that closed from 2023/24 (see the planning areas issue).
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School planning areas are only recorded from 2023/24
The enrolment workbooks only include a School Planning Area column from 2023/24. Schools that closed or amalgamated before then have no planning area.
- What it affects
- Planning-area trends count only schools with a recorded planning area: today's schools and schools that closed from 2023/24. Earlier years are understated, more so further back (nationally about 2.5% of pupils in 2015/16, 7% in 2005/06 and 32% in 1975/76 are in schools with no planning area), and an amalgamation can look like a sudden rise. That is why area changes default to 10 years.
- How this site handles it
- Each school counts in its latest recorded planning area for every year. Schools with no recorded planning area count in national and county totals but in no planning area. Planning-area pages warn about this and show how much of the county is left out.
- Scope
- Planning area figures
- Source notes
- The column appears in the 2023/24, 2024/25 and 2025/26 workbooks. 79 of the 314 planning areas cross county lines.
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Change over 10 years: new roll numbers, young schools and highest years
Change over 10 years compares each school's pupils in the latest year with 10 years earlier. Some schools have no figure for that year, and some were still adding classes then.
- What it affects
- A school with no figure 10 years back may be new, or an existing school under a new roll number, usually after an amalgamation; the files don't say which. A school that opened in the seven years before was still adding classes, so its percentage runs very high. An amalgamation that kept an existing roll number shows as a sudden rise. A school's highest year on record is not its capacity: many schools peaked in the early 1980s.
- How this site handles it
- Schools first recorded with fewer than 50 pupils read 'Opened', others 'Figures start', and neither gets a percentage. Growing or falling means a change of 10% or more. The 'Grown most' and 'Fallen most' lists only rank schools with 50 or more pupils 10 years back that weren't still filling their classes, and only appear where 15 or more schools can be ranked. Tables can also show 5 or 20 years. Find schools counts schools still filling their classes 10 years back as newer schools, as the area pages do. Its totals add up the pupils of the schools with figures for both years, so schools that have closed are left out; most have no map position. That combined change can differ from a county's or planning area's own change: nationally it is −4.2% against −1.8%.
- Scope
- School, county, planning area, irish-medium group and find schools figures
- Source notes
- The enrolment workbooks identify schools by roll number only. They don't record opening dates or amalgamations.
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Teacher numbers after 2015/16 are estimates
Since 2016/17 the Department of Education's class-size files give the number of mainstream classes but no longer count every teacher. From 2019/20 we estimate the rest: the special education and special class teaching posts the NCSE allocates, and a principal (and, in the largest schools, a deputy) who doesn't teach a class where that year's staffing circular gives the school one.
- What it affects
- Teaching posts on school, county, planning-area, Irish-medium and national pages. They count posts, not people, so part of a post can be a teacher shared with another school. Some teachers, such as Home School Community Liaison and supply panel teachers, are in neither source, and allocations are made for the year ahead, so totals run low: about 9% below the Department's payroll count of primary teachers in 2024/25, once special schools are added.
- How this site handles it
- Pages show each part beside the total and call the total an estimate. Class teachers are exact in every year from 2006/07: one for each mainstream class. 2016/17 to 2018/19 show class teachers and the principal only, with a dashed box where the rest would be. A school missing from the NCSE's figures in a year counts only its class teachers and principal. Filters and rankings use class teachers, not the estimate.
- Scope
- School, county, planning area, irish-medium group and national figures
- Source notes
- Principal and deputy thresholds come from Appendix B of the staffing circulars for 2013/14, 2022/23 and 2024/25; each year uses the latest circular at or before it. DEIS bands come from the Department's 2026/27 DEIS list. SNAs are shown alongside but aren't teachers.
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NCSE allocations for 2020/21 to 2022/23 are carried forward
The NCSE's allocation datasets for 2020/21, 2021/22 and 2022/23 each hold its 2023/24 file, so there are no special education figures published for those years. There is also no list of special classes for 2019/20.
- What it affects
- Estimated teaching posts from 2019/20 to 2022/23.
- How this site handles it
- The Department kept special education allocations unchanged in those years (Circulars 0019/2021 and 0020/2022), so 2020/21 and 2021/22 use the 2019/20 allocation and 2022/23 uses the one made in September 2022, published as 2023/24. Special class teachers come from the NCSE's list of special classes for each year. For 2019/20 they are the 2020/21 classes that weren't new that year, in schools that had special-class SNAs in 2019/20.
- Scope
- School, county, planning area, irish-medium group and national figures
- Source notes
- Schools given extra hours during those years, such as new schools or ones granted an exceptional review, may be a little low. The early intervention class lists for 2020/21 and 2021/22 repeat classes already in the main lists, so each class is counted once.
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Some schools recorded extra classes for one year
In 2020/21 26 schools, and in 2021/22 38 schools, recorded two or more extra mainstream classes for a single year before going back, often to exactly one class per standard. The files don't show whether classes were really split or were recorded by standard.
- What it affects
- Class teachers and average class size for those schools in those years.
- How this site handles it
- Figures are shown as published.
- Scope
- School figures
- Source notes
- Other years have at most five schools like this.
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Special schools: a separate list from 2011/12, and gaps in the NCSE's figures
The Department lists special schools separately from mainstream schools from 2011/12. Before that they are in the same full lists as mainstream schools, with nothing to mark them, so a special school can only be followed back if it was still open in 2011/12. The Department publishes only pupils, girls and boys for special schools, not pupils by class or class sizes. The NCSE's allocation datasets for 2020/21, 2021/22 and 2022/23 each hold its 2023/24 file, which also gives 2022/23, so there are no teaching post or SNA figures for 2020/21 and 2021/22.
- What it affects
- Totals across special schools start in 2011/12, while each school's page goes back to 1993/94 where it can. Special schools that closed before 2011/12 aren't shown, and no special school is counted in any mainstream total.
- How this site handles it
- Special schools are kept apart from mainstream schools everywhere on the site. Teaching posts and SNAs are the NCSE's figures for each year as published; where a later file gives an updated figure for a year, such as one at the close of the school year, the later one is used. The 2026/27 file lists a principal and deputy who don't teach a class separately from teaching posts; earlier files don't say how they are counted.
- Scope
- Special school, county, planning area and national figures
- Source notes
- Designations come from the NCSE's list of special schools (August 2024), so newer schools and a few others have none. Some special schools, including hospital schools, aren't in the NCSE's allocation files. In 2025/26 the Department marks one school's figures as not collected the usual way; they are shown as published. Two new schools had no location in 2025/26, so they have no distances.