Summary:
Zip code 06807 (Cos Cob, CT) is served by a single elementary school, Cos Cob School, which enrolls 343 students in grades PK through 5 within the highly ranked Greenwich School District. Cos Cob School stands out as a strong, well-resourced school that consistently outperforms Connecticut state averages in every tested subject, while also maintaining low chronic absenteeism and a favorable 10:1 student-to-teacher ratio. Its statewide rank has improved for three straight years, climbing from 159th to 102nd among roughly 500 Connecticut elementary schools and earning a 4-star rating for 2025–26.
Academically, Cos Cob School is far above state norms but trails its own district in most categories. For example, 3rd grade ELA proficiency is 77.2% versus the state’s 47.3%, but the district average is 83.3%; similarly, 5th grade math proficiency is 65.9% versus the state’s 45.8%, while Greenwich’s average is 77.5%. The school’s biggest challenge is upper-elementary math: 4th grade math proficiency fell sharply from 72.3% to 62.9% in one year, widening the gap with the district to 21 points. That said, the school made significant gains in early literacy, with 3rd grade ELA jumping nearly 19 percentage points between 2024–25 and 2025–26.
Cos Cob School also benefits from a relatively low poverty rate (16% free/reduced lunch eligibility) and substantial per-student spending of $22,254, which aligns with its strong attendance rate of just 6% chronic absenteeism relative to the state’s 16.4%. For parents, this is a high-performing school in an affluent, well-supported community, offering solid academics and a positive trajectory—especially in reading—even though it sits slightly below the exceptional Greenwich district average in math and some upper-grade subjects. Its improving rank and strong resources make it an excellent choice within zip code 06807.
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