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St. Mary's National School

Roll number: 02872U Lamb's Cross, Sandyford, Dublin 18

School details

Address: Lamb's Cross, Sandyford, Dublin 18 (D18XV90)
Email: [email protected]
Phone: 012954173
Principal: Fergus Lyons
Ethos: Catholic
DEIS: N
Irish classification: No subjects through Irish
Gaeltacht: N
Island: N
Local authority: Dun Laoghaire Rathdown
School patron: Archbishop of Dublin
School type: Ordinary
School level: All-Through School
Planning area: Ballinteer_Stepaside_DLR

Class size history

Mainstream class group data is shown separately from standard/year-group enrolment data. The source does not identify which standard/year group each class group belongs to.

Average class size

24.20

2025/26

Mainstream classes

2025/26

Largest class group

2025/26

Classes with 30+ pupils

2025/26

Class group metrics trend

Class group metrics by year

Year	Mainstream class pupils	Mainstream classes	Average class size	Largest class	Classes 30+
2006/07	101	6	16.83	28	0
2007/08	106	6	17.67	28	0
2008/09	126	6	21.00	28	0
2009/10	159	8	19.88	25	0
2010/11	183	9	20.33	26	0
2011/12	212	10	21.20	31	1
2012/13	226	9	25.11	32	1
2013/14	257	9	28.56	34	5
2014/15	260	9	28.89	34	6
2015/16	259	10	25.90	34	3
2016/17	264	10	26.40	34	3
2017/18	263	10	26.30	34	4
2019/20	265	10	26.50	33	4
2020/21	256	10	25.60	34	3
2021/22	249	10	24.90	34	2
2022/23	250	10	25.00	34	3
2023/24	242	10	24.20	31	2
2024/25	244	10	24.40	31	1
2025/26	242	10	24.20	30	1

Data highlights

Key numbers to spot outliers or notable changes.

Biggest gain in a single year: 1982/83: 110 in 1981/82 → 146, +36 pupils.
Biggest loss in a single year: 1993/94: 163 in 1983/84 → 101, -62 pupils.
Largest single-class increase: Junior Infants in 2021/22 (25 → 48, +23).
Largest single-class decrease: 6th Class in 2021/22 (52 → 28, -24).
Largest cohort-step gain: 2nd → 3rd in 2025/26 (43 → 48, +5).
Largest cohort-step loss: JI → SI in 2022/23 (48 → 42, -6).
Overall: 99 (1974/75) → 242 (2025/26), 143.

Summary statistics (class-level data)

Min / max / mean enrolment per class across the available final by-standard years.

Class	Min	Max	Mean	Years
Junior Infants	25	48	33.0	6
Senior Infants	25	42	31.0	6
1st Class	24	42	30.2	6
2nd Class	26	43	30.0	6
3rd Class	26	48	31.3	6
4th Class	24	34	28.0	6
5th Class	28	34	30.2	6
6th Class	25	52	33.5	6
Total	69	265	154.6	43

Total enrolment over time

Total and gender trends use historical records where available. Class-level data starts in 2020/21.

Enrolment by gender over time

Enrolment by class over time

Cohort progression

Base cohort:

Track how each cohort (pupils who were in the same class in the same year) progresses through the school. Each step shows the count; the number between steps is the net change (pupils gained minus pupils lost).

Cohort 2020/21

JI 2020/21 25

SI 2021/22 25

-1

1st 2022/23 24

2nd 2023/24 26

3rd 2024/25 26

-2

4th 2025/26 24

Cohort 2021/22

JI 2021/22 48

-6

SI 2022/23 42

1st 2023/24 42

2nd 2024/25 43

3rd 2025/26 48

Cohort 2022/23

JI 2022/23 31

-3

SI 2023/24 28

-2

1st 2024/25 26

2nd 2025/26 26

Cohort 2023/24

JI 2023/24 30

-1

SI 2024/25 29

-1

1st 2025/26 28

Cohort 2024/25

JI 2024/25 32

-2

SI 2025/26 30

Cohort 2025/26

JI 2025/26 32

Raw data by year

Year	Female	Male	JI	SI	1st	2nd	3rd	4th	5th	6th	Total
1974/75	42	57	–	–	–	–	–	–	–	–	99
1975/76	–	–	–	–	–	–	–	–	–	–	86
1976/77	45	60	–	–	–	–	–	–	–	–	105
1977/78	35	49	–	–	–	–	–	–	–	–	84
1978/79	–	–	–	–	–	–	–	–	–	–	71
1979/80	30	39	–	–	–	–	–	–	–	–	69
1980/81	32	49	–	–	–	–	–	–	–	–	81
1981/82	45	65	–	–	–	–	–	–	–	–	110
1982/83	59	87	–	–	–	–	–	–	–	–	146
1983/84	68	95	–	–	–	–	–	–	–	–	163
1993/94	48	53	–	–	–	–	–	–	–	–	101
1994/95	41	48	–	–	–	–	–	–	–	–	89
1995/96	34	51	–	–	–	–	–	–	–	–	85
1996/97	35	42	–	–	–	–	–	–	–	–	77
1997/98	36	48	–	–	–	–	–	–	–	–	84
1998/99	38	52	–	–	–	–	–	–	–	–	90
1999/00	31	54	–	–	–	–	–	–	–	–	85
2000/01	32	56	–	–	–	–	–	–	–	–	88
2001/02	41	54	–	–	–	–	–	–	–	–	95
2002/03	41	59	–	–	–	–	–	–	–	–	100
2003/04	44	53	–	–	–	–	–	–	–	–	97
2004/05	57	49	–	–	–	–	–	–	–	–	106
2005/06	53	56	–	–	–	–	–	–	–	–	109
2006/07	48	53	–	–	–	–	–	–	–	–	101
2007/08	55	51	–	–	–	–	–	–	–	–	106
2008/09	62	64	–	–	–	–	–	–	–	–	126
2009/10	79	80	–	–	–	–	–	–	–	–	159
2010/11	91	92	–	–	–	–	–	–	–	–	183
2011/12	117	95	–	–	–	–	–	–	–	–	212
2012/13	124	102	–	–	–	–	–	–	–	–	226
2013/14	144	113	–	–	–	–	–	–	–	–	257
2014/15	136	124	–	–	–	–	–	–	–	–	260
2015/16	128	131	–	–	–	–	–	–	–	–	259
2016/17	128	136	–	–	–	–	–	–	–	–	264
2017/18	124	139	–	–	–	–	–	–	–	–	263
2018/19	129	134	–	–	–	–	–	–	–	–	263
2019/20	124	141	–	–	–	–	–	–	–	–	265
2020/21	115	141	25	32	30	27	27	34	29	52	256
2021/22	115	134	48	25	31	28	29	26	34	28	249
2022/23	118	132	31	42	24	30	29	29	31	34	250
2023/24	120	122	30	28	42	26	29	26	30	31	242
2024/25	127	117	32	29	26	43	26	29	28	31	244
2025/26	118	124	32	30	28	26	48	24	29	25	242