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Cos Cob School

Q: Is Cos Cob School a good school?

Cos Cob School ranks 102 nd of 492 Connecticut elementary schools. SchoolDigger rates this school 4 stars out of 5.

Public Grades PK, KG-5

102^nd

SchoolDigger Rank ?

of 492 Connecticut Elementary Schools

Better than 79% of Connecticut elementary schools

Summary

Cos Cob School is a public elementary school in Cos Cob, Connecticut, serving 343 students in grades PK-5 within the Greenwich School District. On the most recent statewide ranking, Cos Cob School placed 102nd out of 491 Connecticut elementary schools (79th percentile, 4 stars) — a solid performance that puts it well above the state average in every subject. However, within its own district, Cos Cob ranks 7th of 8 nearby elementary schools, largely because it is surrounded by exceptional peers like North Mianus School (ranked 1st) and Riverside School (ranked 2nd) in the state. This "Greenwich paradox" means families get a strong, above-average school that is nonetheless among the more modest performers in one of Connecticut's highest-achieving districts.

The most notable academic challenge is mathematics. In 4th grade, Cos Cob's math proficiency rate (62.9%) trails the district average (83.9%) by 21 points and is roughly 25–30 points behind top peers like North Mianus and Riverside; a similar pattern appears in 5th grade. English Language Arts scores are also below the district average but closer to it. Cos Cob serves a more socioeconomically diverse population than most of its immediate neighbors, with 16.0% of students eligible for free/reduced-price lunch — compared to under 3% at Riverside and Old Greenwich School, though far below Hamilton Avenue School's 59.9%. The school also boasts excellent attendance: a 6.0% chronic absenteeism rate, better than the district (8.5%) and far better than the state (16.4%).

There is positive momentum worth noting. Cos Cob's ranking jumped from 156th to 102nd in a single year, and its special education students scored at the 91st percentile statewide — a remarkable result. The school also dramatically outperforms nearby Stamford schools like Stillmeadow School and Westover School, where proficiency rates are often 30–40 points lower. With a favorable student–teacher ratio of 10.0 and the full resources of the Greenwich district behind it, Cos Cob is well-positioned to continue closing the gap with its higher-ranked neighbors.

343

Students ?

10.0

Student/teacher ratio ?

$30,090

Per pupil spending ?

16.0%

Free/reduced lunch eligible (2024-25) ?

98.4%

Kindergartners with all required vaccines (2025-26)

Exemptions: 0% (any vaccine)

300 East Putnam Ave.
Cos Cob, CT 06807

(203) 869-4670

District: Greenwich School District

Students who attend Cos Cob School usually attend:

Middle:	Central Middle School
High:	Greenwich High School

Racial breakdown:

White:

67.3%

Hispanic:

20.4%

Asian:

5.2%

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Compare Cos Cob School to nearby elementary schools!

At a glance

▲ Ranking trend: Improving — 71st percentile in 2016 → 79th in 2026

Strengths

✓Test scores above the Connecticut average (72% vs 51% meeting standards)

✓Ranks in the top 21% of Connecticut elementary schools

✓Ranking is trending up — up 8 percentile points since 2016

Worth a look

!Near the bottom of Greenwich School District's ranking

Students meeting standards (2025-2026) ?

This school72%

District avg82%

Connecticut avg51%

102^nd of 492

Connecticut public elementary schools ?

Top 21%▲ up 8 pts since 2016

From top 29% (2016) to top 21% (2026)

See the entire ranking list of Connecticut Elementary Schools →

★★★★★

SchoolDigger rating ?

9^th of 11Elementary Schools in the Greenwich School District

14^th of 153Greenwich School District among Connecticut districts

Statewide rank percentile over time (100 = the top-ranked school in the state; click a legend item to add a student group)

Show full rank history (all student groups)

All Students

Year	Avg score	Statewide rank	Connecticut percentile	Rating
2026	80.8	102 of 492	79.3%	★★★★☆
2025	73.0	156 of 493	68.4%	★★★☆☆
2024	72.0	159 of 497	68.0%	★★★☆☆
2023	77.0	131 of 491	73.3%	★★★★☆
2022	75.1	134 of 490	72.7%	★★★★☆
2021	81.7	110 of 538	79.6%	★★★★☆
2019	79.8	123 of 522	76.4%	★★★★☆
2018	74.0	156 of 532	70.7%	★★★★☆
2017	75.5	147 of 519	71.7%	★★★★☆
2016	73.3	150 of 518	71.0%	★★★★☆
2015	73.8	177 of 551	67.9%	★★★☆☆
2013	75.2	164 of 557	70.6%	★★★★☆
2012	70.8	210 of 564	62.8%	★★★☆☆
2011	75.1	158 of 565	72.0%	★★★★☆
2010	70.6	212 of 579	63.4%	★★★☆☆
2009	72.9	190 of 566	66.4%	★★★☆☆
2008	71.8	201 of 565	64.4%	★★★☆☆
2007	70.7	223 of 568	60.7%	★★★☆☆
2006	69.8	223 of 570	60.9%	★★★☆☆

Female

Year	Avg score	Statewide rank	Connecticut percentile	Rating
2023	75.8	76 of 230	67.0%	★★★☆☆
2022	70.0	94 of 234	59.8%	★★★☆☆
2021	80.0	93 of 455	79.6%	★★★★☆
2019	66.2	100 of 242	58.7%	★★★☆☆
2018	65.8	109 of 259	57.9%	★★★☆☆

Male

Year	Avg score	Statewide rank	Connecticut percentile	Rating
2023	72.6	82 of 231	64.5%	★★★☆☆
2022	69.6	93 of 232	59.9%	★★★☆☆
2021	76.9	109 of 445	75.5%	★★★★☆
2018	67.4	111 of 262	57.6%	★★★☆☆

Special Education

Year	Avg score	Statewide rank	Connecticut percentile	Rating
2021	85.6	32 of 371	91.4%	★★★★★

White

Year	Avg score	Statewide rank	Connecticut percentile	Rating
2026	68.0	87 of 246	64.6%	★★★☆☆
2025	46.2	160 of 248	35.5%	★★☆☆☆
2024	47.8	162 of 250	35.2%	★★☆☆☆
2023	61.8	116 of 262	55.7%	★★★☆☆
2022	64.5	105 of 252	58.3%	★★★☆☆
2021	70.5	92 of 327	71.9%	★★★★☆
2019	66.6	98 of 295	66.8%	★★★☆☆
2018	57.2	144 of 296	51.4%	★★★☆☆

How student groups rank statewide ? (each group's percentile vs the same group at other schools — higher is better; the +/- beside each compares the group with this school's overall percentile)

Special Education (2021)91st percentile+12 vs school

Female (2023)67th percentile-6 vs school

White (2026)65th percentile-15 vs school

Male (2023)65th percentile-9 vs school

By subject vs Connecticut (2025-2026) ?

Science77%+24 vs state

English Language Arts73%+22 vs state

Mathematics69%+19 vs state

★

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Schools Near Cos Cob School

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Ranking:

E Elementary M Middle H High A Alternative P Private

Choose columns to see: Summary School Students/Teachers Ranking Test Scores Vaccination Finance All

School													Students/Teachers											Ranking (2026)				Ranking (2025)				NGSS Science (2026)		SBAC English Language Arts (2026)						SBAC Mathematics (2026)						Vaccination (2025-26)		Per Pupil Expenditures (2025)
Name	Type	Grades	Address	City	Zip	County	District	Is Charter	Is Magnet	Is Virtual	Is Title I	Phone	Enrollment	Full-time Teachers	Student/ Teacher Ratio	Free/reduced lunch (2024-25)	White	Black	Hispanic	Asian	American Indian	Pacific Islander	Two or More Races	Average Standard Score (2026)	Statewide Rank (2026)	State Percentile (2026)	SchoolDigger Rating (2026)	Average Standard Score (2025)	Statewide Rank (2025)	State Percentile (2025)	Rank Change from Previous Year	NGSS Science 5th Grade	NGSS Science 8th Grade	SBAC English Language Arts 3rd Grade	SBAC English Language Arts 4th Grade	SBAC English Language Arts 5th Grade	SBAC English Language Arts 6th Grade	SBAC English Language Arts 7th Grade	SBAC English Language Arts 8th Grade	SBAC Mathematics 3rd Grade	SBAC Mathematics 4th Grade	SBAC Mathematics 5th Grade	SBAC Mathematics 6th Grade	SBAC Mathematics 7th Grade	SBAC Mathematics 8th Grade	Vaccination: Kindergartners with all required vaccines	Vaccination: Exemption rate	Total
Cos Cob School	Public	PK, KG-5	300 East Putnam Ave.	Cos Cob	06807	Western Connecticut Planning Region	Greenwich School District	No	No	No	No	(203) 869-4670	343	34	10.0	16.0%	231 (67.3%)	4 (1.2%)	70 (20.4%)	18 (5.2%)	2 (0.6%)	0 (0.0%)	18 (5.2%)	80.8	102^nd of 492 public elementary schools	79.3%		73	156^th of 493 public elementary schools	68.4%	54	77.3		77.2	69.4	72.7				77.2	62.9	65.9				98.4%	0%	$30,090
Riverside School	Public	K-5	90 Hendrie Ave.	Riverside	06878	Western Connecticut Planning Region	Greenwich School District	No	No	No	No	(203) 637-1440	440	37	11.7	1.6%	314 (71.4%)	0 (0.0%)	80 (18.2%)	23 (5.2%)	1 (0.2%)	0 (0.0%)	22 (5.0%)	95.6	2^nd of 492 public elementary schools	99.6%		96.1	3^rd of 493 public elementary schools	99.4%	1	85.1		87.5	2584.0	91.9				94.4	2588.0	87.8				100%	0%	$25,196
Julian Curtiss School	Public	PK, KG-5	180 East Elm St.	Greenwich	06830	Western Connecticut Planning Region	Greenwich School District	No	No	No	Yes	(203) 869-1896	236	28	8.3	39.0%	100 (42.4%)	12 (5.1%)	81 (34.3%)	21 (8.9%)	0 (0.0%)	0 (0.0%)	22 (9.3%)	85	73^rd of 492 public elementary schools	85.2%		84	73^rd of 493 public elementary schools	85.2%		516.0		87.1	72.4	73.8				2519.0	86.2	64.3				100%	0%	$34,301
International School At Dundee	Public	K-5	55 Florence Rd.	Riverside	06878	Western Connecticut Planning Region	Greenwich School District	No	No	No	No	(203) 637-3800	342	30	11.2	10.5%	157 (45.9%)	3 (0.9%)	64 (18.7%)	87 (25.4%)	0 (0.0%)	0 (0.0%)	31 (9.1%)	92.4	17^th of 492 public elementary schools	96.5%		91.6	19^th of 493 public elementary schools	96.1%	2	78.8		87.9	85.5	78.8				2539.0	85.5	86.5				98.3%	0%	$27,915
North Mianus School	Public	K-5	309 Palmer Hill Rd.	Riverside	06878	Western Connecticut Planning Region	Greenwich School District	No	No	No	No	(203) 637-9730	423	41	10.2	2.8%	277 (65.5%)	2 (0.5%)	53 (12.5%)	60 (14.2%)	1 (0.2%)	0 (0.0%)	30 (7.1%)	96.4	1^st of 492 public elementary schools	99.8%		96.3	1^st of 493 public elementary schools	99.8%		89.9		94.9	90.4	89.9				2569.0	91.6	92.4				100%	0%	$25,677
North Street School	Public	PK, KG-5	381 North St.	Greenwich	06830	Western Connecticut Planning Region	Greenwich School District	No	No	No	No	(203) 869-6756	411	38	10.8	4.4%	306 (74.5%)	3 (0.7%)	56 (13.6%)	18 (4.4%)	0 (0.0%)	1 (0.2%)	27 (6.6%)	94	8^th of 492 public elementary schools	98.4%		93.8	8^th of 493 public elementary schools	98.4%		83.7		85.3	94.5	86.0				89.3	87.3	76.7				98.4%	0%	$24,905
Old Greenwich School	Public	PK, KG-5	825 Sound Beach Ave.	Old Greenwich	06870	Western Connecticut Planning Region	Greenwich School District	No	No	No	No	(203) 637-0150	385	37	10.5	2.3%	323 (83.9%)	0 (0.0%)	29 (7.5%)	15 (3.9%)	0 (0.0%)	0 (0.0%)	18 (4.7%)	93	12^th of 492 public elementary schools	97.6%		95.7	4^th of 493 public elementary schools	99.2%	8	84.5		86.6	86.4	79.3				92.5	90.9	74.1				100%	0%	$26,372
Westover School	Public	K-7	412 Stillwater Ave.	Stamford	06902	Western Connecticut Planning Region	Stamford School District	No	No	No	Yes	(203) 977-4572	624	57	11.0	60.1%	116 (18.6%)	109 (17.5%)	299 (47.9%)	69 (11.1%)	1 (0.2%)	0 (0.0%)	30 (4.8%)	31.3	329^th of 492 public elementary schools	33.1%		35.1	304^th of 493 public elementary schools	38.3%	25	45.6		41.7	36.3	51.7	45.9	38.5		38.5	35.2	34.8	27.1	32.1		100%	0%	$24,829
Hamilton Avenue School	Public	PK, KG-5	184 Hamilton Avenue	Greenwich	06830	Western Connecticut Planning Region	Greenwich School District	No	No	No	Yes	(203) 869-1685	299	38	7.9	59.9%	92 (30.8%)	13 (4.3%)	167 (55.9%)	9 (3.0%)	3 (1.0%)	0 (0.0%)	15 (5.0%)	72.9	161^st of 492 public elementary schools	67.3%		69.2	177^th of 493 public elementary schools	64.1%	16	499.0		71.0	68.6	2524.0				58.1	2547.0	2561.0				94.4%	2.8%	$33,736
Stamford Charter School for Excellence	Public, Charter	PK, KG-8	1 Schuyler Ave.	Stamford	06902	Western Connecticut Planning Region	Stamford Charter School for Excellence District	Yes	No	No	Yes	(203) 989-0000	543	19	28.5	55.6%	15 (2.8%)	219 (40.3%)	170 (31.3%)	118 (21.7%)	4 (0.7%)	1 (0.2%)	16 (2.9%)	75.9	146^th of 492 public elementary schools	70.3%		84.8	69^th of 493 public elementary schools	86.0%	77	50.9	63.6	78.9	88.9	69.5	61.1	66.7	77.8	77.2	88.7	47.5	55.6	52.9	2608.0	75.8%	0%	$11,837

Frequently Asked Questions about Cos Cob School

How many students attend Cos Cob School?

In the 2024-25 school year, 343 students attended Cos Cob School.

What schools do graduates of Cos Cob School attend?

Students who attend Cos Cob School usually go on to attend:

Middle : Central Middle School
High : Greenwich High School

What is the racial makeup of Cos Cob School?

Students at Cos Cob School are 67% White, 20% Hispanic, 5% Asian, 5% Two or more races, 1% African American.

Is Cos Cob School a good school?

Cos Cob School ranks 102^nd of 492 Connecticut elementary schools. SchoolDigger rates this school 4 stars out of 5.

What district is Cos Cob School in?

Greenwich School District

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Latest Connecticut data All new data »

2017–18 through 2025–26 immunization rates (updated)NewOct 19, 2026

2024–25 through 2025–26 attendance data & graduation ratesAug 31, 2026

2025–26 NGSS, SAT & SBAC test scoresAug 31, 2026

2024–25 school spending dataApr 2, 2026

SchoolDigger data sources: National Center for Education Statistics, U.S. Department of Education, the U.S. Census Bureau and the Connecticut Department of Education.

IMPORTANT DISCLAIMERS: Not all boundaries are included. We make every effort to ensure that boundaries are up-to-date. But it's important to note that these are approximations and are for general informational purposes only. To verify legal descriptions of boundaries or school locations, contact your local tax assessor's office and/or school district.