S N San Treasa
Mount Merrion · Roll number 18647D
- Catholic ethos
- Not DEIS
- Pupils in 2025/26
- 430
- +5 on 2024/25
- Over 10 years
- −6%
- Down 26 from 456 in 2015/16
- Girls and boys
- 210 / 220
- 49% girls
Pupils since 1974
Total enrolment each school year
Shaded: the last 10 years, 2015/16 to 2025/26. 1983/84 is left out because its source file is incomplete, and no files exist for 1984/85 to 1992/93. Known data issues
Pupils by class
Published for each class from 2020/21.
This year, 2025/26
430 pupils across 8 classes
Every class, every year
Darker cells have more pupils. A group of pupils moves down one class and right one year.
| 2020/21 | 2021/22 | 2022/23 | 2023/24 | 2024/25 | 2025/26 | Average | |
|---|---|---|---|---|---|---|---|
| Junior Infants | 58 | 57 | 58 | 54 | 58 | 58 | 57.2 |
| Senior Infants | 57 | 57 | 55 | 57 | 52 | 57 | 55.8 |
| 1st Class | 58 | 57 | 57 | 56 | 56 | 56 | 56.7 |
| 2nd Class | 57 | 55 | 53 | 56 | 56 | 55 | 55.3 |
| 3rd Class | 53 | 53 | 54 | 51 | 52 | 51 | 52.3 |
| 4th Class | 48 | 54 | 53 | 51 | 49 | 53 | 51.3 |
| 5th Class | 50 | 50 | 52 | 55 | 50 | 49 | 51.0 |
| 6th Class | 51 | 45 | 43 | 48 | 52 | 51 | 48.3 |
JI and SI are Junior and Senior Infants.
Started Junior Infants in 2024/25
58 in Junior Infants (2024/25), 57 in Senior Infants (2025/26): 1 pupil fewer.
- 58Junior Infants2024/25
- 57Senior Infants2025/26
Started Junior Infants in 2023/24
54 in Junior Infants (2023/24), 56 in 1st Class (2025/26): 2 pupils more.
- 54Junior Infants2023/24
- 52Senior Infants2024/25
- 561st Class2025/26
Started Junior Infants in 2022/23
58 in Junior Infants (2022/23), 55 in 2nd Class (2025/26): 3 pupils fewer.
- 58Junior Infants2022/23
- 57Senior Infants2023/24
- 561st Class2024/25
- 552nd Class2025/26
Started Junior Infants in 2021/22
57 in Junior Infants (2021/22), 51 in 3rd Class (2025/26): 6 pupils fewer.
- 57Junior Infants2021/22
- 55Senior Infants2022/23
- 561st Class2023/24
- 562nd Class2024/25
- 513rd Class2025/26
Started Junior Infants in 2020/21
58 in Junior Infants (2020/21), 53 in 4th Class (2025/26): 5 pupils fewer.
- 58Junior Infants2020/21
- 57Senior Infants2021/22
- 571st Class2022/23
- 562nd Class2023/24
- 523rd Class2024/25
- 534th Class2025/26
In Senior Infants in 2020/21
57 in Senior Infants (2020/21), 49 in 5th Class (2025/26): 8 pupils fewer.
- 57Senior Infants2020/21
- 571st Class2021/22
- 532nd Class2022/23
- 513rd Class2023/24
- 494th Class2024/25
- 495th Class2025/26
In 1st Class in 2020/21
58 in 1st Class (2020/21), 51 in 6th Class (2025/26): 7 pupils fewer.
- 581st Class2020/21
- 552nd Class2021/22
- 543rd Class2022/23
- 514th Class2023/24
- 505th Class2024/25
- 516th Class2025/26
In 2nd Class in 2020/21
57 in 2nd Class (2020/21), 52 in 6th Class (2024/25): 5 pupils fewer.
- 572nd Class2020/21
- 533rd Class2021/22
- 534th Class2022/23
- 555th Class2023/24
- 526th Class2024/25
In 3rd Class in 2020/21
53 in 3rd Class (2020/21), 48 in 6th Class (2023/24): 5 pupils fewer.
- 533rd Class2020/21
- 544th Class2021/22
- 525th Class2022/23
- 486th Class2023/24
In 4th Class in 2020/21
48 in 4th Class (2020/21), 43 in 6th Class (2022/23): 5 pupils fewer.
- 484th Class2020/21
- 505th Class2021/22
- 436th Class2022/23
In 5th Class in 2020/21
50 in 5th Class (2020/21), 45 in 6th Class (2021/22): 5 pupils fewer.
- 505th Class2020/21
- 456th Class2021/22
Biggest one-year changes in a class
- +64th Class in 2021/22 (48 to 54)
- −66th Class in 2021/22 (51 to 45)
Class sizes
Mainstream class groups, 2006/07 to 2025/26.
Why these won't match pupils by class
Mainstream class groups only. The source does not identify which standard/year group each class group belongs to. So these figures won't match the pupils-by-class figures exactly.
In 2025/26. Choose a figure to chart it.
Class sizes over time
Average class size, 2006/07 to 2025/26
Teachers
Who teaches at S N San Treasa, 2006/07 to 2025/26.
How we count teachers
Class teachers come from the Department of Education's class sizes: one for each mainstream class. Special education and special class teachers are the posts the National Council for Special Education (NCSE) allocates. We add a principal who doesn't teach a class where the Department's rules give the school one. These are posts, not people: part of a post can be a teacher shared with another school. Up to 2015/16 the Department counted every teacher itself. Known data issues
In 2025/26
22.9teaching posts
Our estimate: about 23 teachers.
- Class teachersOne for each of the 16 mainstream classes 16
- PrincipalRuns the school and doesn't teach a class 1
- Special education teachers147.5 hours of support teaching a week 5.9
5 special needs assistants (SNAs) also work with pupils.
The NCSE has allocated 6 special education teachers, 1 special class teacher and 7 SNAs for next year.
Teachers since 2006/07
Teachers each school year, by role
To 2015/16: the Department of Education's count of every teacher. From 2019/20: our estimate, from class sizes and the NCSE's allocations. Dashed boxes: no special education figures were published for those years, so only class teachers and the principal are shown. Known data issues
Sources: Department of Education class sizes and teacher counts; NCSE school allocations and special classes (CC BY 4.0).
Nearby schools
The 6 primary schools closest to S N San Treasa, measured in a straight line. Pupil numbers are for 2025/26.
| Number on map | School | Distance | Pupils | Since 2015/16 |
|---|---|---|---|---|
| S N San TreasaThis school | – | 430 |
−5.7%
|
|
| 1 | Oatlands Primary School, An Edmund Rice School0.5 km · Blackrock | 0.5 km | 428 |
−0.7%
|
| 2 | Gaelscoil Laighean0.7 km · Baile Átha Cliath 14 · Gaelscoil · Multi-denominational | 0.7 km | 130 | – |
| 3 | S N Naomh Lorcan0.7 km · Stillorgan · Boys | 0.7 km | 390 |
−12.2%
|
| 4 | S N Cnoc Ainbhil0.8 km · Stillorgan · Girls | 0.8 km | 434 |
−6.9%
|
| 5 | Our Lady of Mercy Convent School1.3 km · Booterstown · Girls | 1.3 km | 247 |
+1.2%
|
| 6 | St Brigids N S1.4 km · Stillorgan · Church of Ireland | 1.4 km | 100 |
+1.0%
|
About this school
Inspection reports open on gov.ie, under the name the school had when it was inspected. They describe specific areas of the school's work rather than giving an overall grade. Newer schools may not have one yet.
Contact
- Principal
- Frances Mullin
- Phone
- 012881505
- [email protected]
- Address
- The Rise, Mount Merrion, Co. Dublin, A94 EK75
School
- Ethos
- Catholic
- Patron
- Archbishop of Dublin
- School type
- Ordinary
- School level
- All Through
- DEIS
- Not DEIS
Language and area
- Irish classification
- No subjects through Irish
- Gaeltacht
- Non-Gaeltacht
- Island
- Not on an island
- Local authority
- Dun Laoghaire Rathdown
- Planning area
- Booterstown–Blackrock
Each detail is the latest one the Department of Education has recorded for this school. If a detail was left blank in 2025/26, we show it from an earlier year, so some details may be older than the pupil numbers. Known data issues
Data by year
43 school years from 1974/75 to 2025/26. Class figures start in 2020/21.
| Year | Total | Girls | Boys | JI | SI | 1st | 2nd | 3rd | 4th | 5th | 6th |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2025/26 | 430 | 210 | 220 | 58 | 57 | 56 | 55 | 51 | 53 | 49 | 51 |
| 2024/25 | 425 | 213 | 212 | 58 | 52 | 56 | 56 | 52 | 49 | 50 | 52 |
| 2023/24 | 428 | 214 | 214 | 54 | 57 | 56 | 56 | 51 | 51 | 55 | 48 |
| 2022/23 | 425 | 221 | 204 | 58 | 55 | 57 | 53 | 54 | 53 | 52 | 43 |
| 2021/22 | 428 | 224 | 204 | 57 | 57 | 57 | 55 | 53 | 54 | 50 | 45 |
| 2020/21 | 432 | 219 | 213 | 58 | 57 | 58 | 57 | 53 | 48 | 50 | 51 |
| 2019/20 | 444 | 212 | 232 | – | – | – | – | – | – | – | – |
| 2018/19 | 452 | 216 | 236 | – | – | – | – | – | – | – | – |
| 2017/18 | 452 | 211 | 241 | – | – | – | – | – | – | – | – |
| 2016/17 | 459 | 210 | 249 | – | – | – | – | – | – | – | – |
| 2015/16 | 456 | 208 | 248 | – | – | – | – | – | – | – | – |
| 2014/15 | 453 | 202 | 251 | – | – | – | – | – | – | – | – |
| 2013/14 | 444 | 200 | 244 | – | – | – | – | – | – | – | – |
| 2012/13 | 447 | 201 | 246 | – | – | – | – | – | – | – | – |
| 2011/12 | 449 | 199 | 250 | – | – | – | – | – | – | – | – |
| 2010/11 | 443 | 205 | 238 | – | – | – | – | – | – | – | – |
| 2009/10 | 444 | 210 | 234 | – | – | – | – | – | – | – | – |
| 2008/09 | 449 | 212 | 237 | – | – | – | – | – | – | – | – |
| 2007/08 | 452 | 221 | 231 | – | – | – | – | – | – | – | – |
| 2006/07 | 455 | 225 | 230 | – | – | – | – | – | – | – | – |
| 2005/06 | 462 | 231 | 231 | – | – | – | – | – | – | – | – |
| 2004/05 | 472 | 240 | 232 | – | – | – | – | – | – | – | – |
| 2003/04 | 475 | 229 | 246 | – | – | – | – | – | – | – | – |
| 2002/03 | 488 | 243 | 245 | – | – | – | – | – | – | – | – |
| 2001/02 | 496 | 248 | 248 | – | – | – | – | – | – | – | – |
| 2000/01 | 488 | 247 | 241 | – | – | – | – | – | – | – | – |
| 1999/00 | 493 | 234 | 259 | – | – | – | – | – | – | – | – |
| 1998/99 | 520 | 251 | 269 | – | – | – | – | – | – | – | – |
| 1997/98 | 510 | 245 | 265 | – | – | – | – | – | – | – | – |
| 1996/97 | 503 | 253 | 250 | – | – | – | – | – | – | – | – |
| 1995/96 | 472 | 249 | 223 | – | – | – | – | – | – | – | – |
| 1994/95 | 459 | 234 | 225 | – | – | – | – | – | – | – | – |
| 1993/94 | 422 | 215 | 207 | – | – | – | – | – | – | – | – |
| 1983/84 | 282 | 182 | 100 | – | – | – | – | – | – | – | – |
| 1982/83 | 288 | 188 | 100 | – | – | – | – | – | – | – | – |
| 1981/82 | 275 | 185 | 90 | – | – | – | – | – | – | – | – |
| 1980/81 | 261 | 183 | 78 | – | – | – | – | – | – | – | – |
| 1979/80 | 263 | 177 | 86 | – | – | – | – | – | – | – | – |
| 1978/79 | 69 | – | – | – | – | – | – | – | – | – | – |
| 1977/78 | 298 | 206 | 92 | – | – | – | – | – | – | – | – |
| 1976/77 | 294 | – | – | – | – | – | – | – | – | – | – |
| 1975/76 | 311 | – | – | – | – | – | – | – | – | – | – |
| 1974/75 | 338 | 267 | 71 | – | – | – | – | – | – | – | – |