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William Sidney Mount Elementary School
PublicElementaryGrades PK–6
50 Dean Ln, Stony Brook, NY 11790 · (631) 730-4300 · Part of Three Village Central School District
Students
525
Students per teacher
13:1
Free or reduced lunch
20%
Setting
Suburb
Grades
PK–6
What stands out about William Sidney Mount Elementary School
- Math proficiency 11 pts above the state
- Enrollment up 15.4% since 2020
- Next stop for Setauket kids: 2 schools
On the path
Where Setauket kids come from and go next.
PK–6William Sidney Mount Elementary SchoolYou are here
7–92 schoolsDepends on your address
Test scores
EDFacts via Urban Institute Education Data Portal (SY2020-21) · 2020–21Math proficiency67%
State average 56.1%
Reading / language arts67%
State average 62.6%
Location
Directions ↗
50 Dean Ln, Stony Brook
Students
Enrollment by grade
Pre-K39
Kindergarten61
Grade 161
Grade 261
Grade 374
Grade 481
Grade 575
Grade 673
Enrollment over time
455’20
470’21
511’22
514’23
525’24
Up 15.4% since 2020.
Who goes here
White 55%Asian 24%Hispanic 14%Two or more races 5%Black 1%
As reported to NCES, share of students with a reported race or ethnicity.
What neighbors say
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Parents talk
Conversations in Town Square that mention William Sidney Mount Elementary School.
Other schools in Three Village Central School District
School facts: U.S. Department of Education (NCES), 2024-2025 school year. Scores: EDFacts via Urban Institute Education Data Portal (SY2020-21). The School Grade is our own summary of state test results. Neighbor ratings are opinions, not an official measure of school quality.