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SCHOOL COMMUNITY·THREE VILLAGE CENTRAL SCHOOL DISTRICT·NCES 362820003810

WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL

50 DEAN LN, STONY BROOK, NY 11790 · (631) 730-4300 · Suffolk County
GRADES PK–06ELEMENTARY21-SUBURBREGULAR SCHOOL525 STUDENTS
B
allk12 Grade
Scored higher than 59% of New York public elementary schools
  • B+Test scores Share of students meeting the state standard in reading, math, and other tested subjects, 2023-24 and 2024-25.
  • B-Beats expectations How far test scores land above or below what the share of low-income students predicts for a school in this state.
  • ·Three-year trend Not available for this school, so the grade uses the other parts.

Grades compare a school only with schools in the same state, because every state gives its own test. How grades work · Top-graded New York public elementary schools

Enrollment
525
Elementary
DISTRICT 576 · STATE 443
Student : Teacher
13.1:1
40 FTE teachers
DISTRICT 12.2:1 · STATE 12.8:1
Free / Reduced Lunch
20%
107 students
DISTRICT 15% · STATE 58%
Community
1
0 members
Enrollment and student:teacher ratio compared against other elementary schools. Free/Reduced Lunch and demographics compared against all schools.

Enrollment by grade, 2024-25

GradeStudentsShare
Pre-K397%
Kindergarten6112%
Grade 16112%
Grade 26112%
Grade 37414%
Grade 48115%
Grade 57514%
Grade 67314%

This year's kindergarten class (61) is 16% smaller than its 6th grade class (73).

Student demographics
61%Diversity index
The chance that two students picked at random belong to different racial or ethnic groups.
DISTRICT 52% · STATE 72% · US 70%
White
28955%
DISTRICT 66% · STATE 39% · US 43%
Hispanic
7414%
DISTRICT 12% · STATE 31% · US 30%
Black
61%
DISTRICT 2% · STATE 16% · US 15%
Asian
12824%
DISTRICT 16% · STATE 10% · US 6%
Two+
285%
DISTRICT 5% · STATE 4% · US 5%
Student head counts by race/ethnicity from federal NCES enrollment data. District, state, and US figures are each group's share of all public school students in that area (US excludes territories). Very small groups may be suppressed in the source, so categories do not always sum exactly to total enrollment.
Gender split
Male
26851%
Female
25749%

Discussions

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Test scores

NYS Assessments 2024-25 . % Proficient (Level 3 + Level 4)
English Language Arts
59.0%
NY avg 58.3% . +5.0pp since 2023
Math
67.0%
NY avg 57.4% . +5.0pp since 2023

What this means: On the NYS Assessments, New York's statewide test, about 59 of every 100 students at this school read and write at grade level and about 67 of 100 do math at grade level. Across all New York schools, those numbers are about 58 and 57. Reading and writing scores are up about 5 points since 2023, while math scores are up about 5 points.

NYS Assessments results by year

School yearEnglish Language ArtsMath
2024-2559.0%67.0%
2023-2454.0%62.0%
% Proficient (Level 3 + Level 4), all students and all tested grades.
Source: NYS Assessments. All students, all grades. See all years and grades →

BeatsExpectations

Demographically-adjusted score · methodology
Tier
AS EXPECTED
Performing as predicted given the school's student profile
Actual proficiency
61.0%
composite math + reading, all grades
Predicted
67.5%
based on NY schools with similar FRL share
Beats by
-6.5pp
below demographic expectation

What this means: About 61% of students here test proficient in math and reading, compared with the roughly 68% typical for New York schools with a similar share of low-income students. BeatsExpectations measures results against demographically similar schools rather than by raw scores, and this school falls within the typical range, neither among New York's top nor bottom 10%.

BeatsExpectations runs a per-state regression of proficiency on free/reduced-lunch share, then scores each school by residual. How this is calculated →

Schools most like WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL

WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL's state test result (61.0% proficient) is higher than 0 of the 5 schools below with a result.

SchoolStudentsLow-incomeProficient
WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL this school52520.4%61.0%
SKANO ELEMENTARY SCHOOL
CLIFTON PARK
52418.7%75.7%
JOHN STREET SCHOOL
FRANKLIN SQUARE
48319.7%68.9%
EAST HILLS ELEMENTARY SCHOOL
ROSLYN HEIGHTS
55220.8%80.0%
PS 199 JESSIE ISADOR STRAUS
NEW YORK
57023.9%78.6%
GUILDERLAND ELEMENTARY SCHOOL
GUILDERLAND
47025.1%67.0%
Matched among New York elementary schools on enrollment, the share of students from low-income families (eligible for free or reduced-price lunch), and racial and ethnic makeup. Proficient is the average share of students meeting the state standard across all of the school's state tests in 2023-24 and 2024-25, the same combined score our test-score rankings use. Online schools and schools serving specialized populations are not matched.

Where WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL ranks

Among elementary schools
MeasureThis schoolIn New YorkIn Suffolk County
State test proficiency
ranked highest first
61.0%#716 of 2,335#42 of 168
Math proficiency
ranked highest first
67.0%#828 of 2,342
▲ 39
#54 of 169
no change
Reading proficiency
ranked highest first
59.0%#1,006 of 2,343
▼ 265
#62 of 169
▼ 24
Enrollment
ranked largest first
525#716 of 2,585#66 of 209
Students per teacher
ranked fewest first
13.1:1#1,643 of 2,338#146 of 196
Diversity index
ranked most diverse first
61.5%#641 of 2,388#55 of 197
Free and reduced lunch
ranked highest share first
20.4%#2,222 of 2,534#143 of 200
Enrollment change since 2017-18
ranked fastest growth first
+10.3%#261 of 606#22 of 57
Ranked against other public elementary schools. Online schools are left out of every list, and test-score lists leave out schools that serve specialized populations. Each rank links to the full list. Arrows under a test-score rank show places moved since the prior test year, among schools tested both years.

4-year change

SY 2020-21 vs SY 2024-25
Enrollment
525
+70 (+15%) vs 2020
-14% since 1990-91, when it was 614
Student : Teacher
13.1:1
was 12.0:1
Source: NCES Common Core of Data

Enrollment and staffing by year

School yearStudentsTeachers (FTE)Students per teacherFree and reduced lunch
2024-2552540.213.1:120% (107)
2023-2451437.813.6:120% (103)
2022-235114212.2:117% (88)
2020-214553812.0:112% (56)
2017-184763214.9:10% (0)
2015-165553615.4:15% (26)
2010-117235413.4:13% (21)
2000-018815715.5:12% (16)
1990-916144413.9:1N/A
Source: NCES Common Core of Data. Rows are the federal collections on file for WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL.

About WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL

WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL is a mid-sized elementary school with an address in STONY BROOK, New York. It teaches 525 students in pre-K through 6.

WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL is one of 8 schools in THREE VILLAGE CENTRAL SCHOOL DISTRICT, which enrolls 5,629 students in total.

The student body at WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL is 55% White. Beyond that, enrollment is 24% Asian, 14% Hispanic, and 5% multiracial. The White share of the county population is higher, at 66%. Its diversity index, the chance that two randomly chosen students belong to different racial or ethnic groups, is 61%.

WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL lists 40.2 full-time-equivalent teachers; that is about 13.1 students per teacher. The 12.8:1 average for elementary schools in New York is close to this figure. About 20% of students at WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL are eligible for free or reduced-price lunch. The average for public schools in Suffolk County is 39%.

WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL holds a B allk12 Grade, placing it above 59% of New York public elementary schools.

The BeatsExpectations prediction for WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL is 67.5%, and its average proficiency rate across its state test results is 61.0%.

Suffolk County is the school's county. There, median household income comes to about $130,686, the share of adults with a bachelor's degree or higher is 40%, and about 4% of people live in poverty. Suffolk County's 343 public schools enroll about 222,439 students and include WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL.

WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL's closest public school neighbor is ROBERT CUSHMAN MURPHY JUNIOR HIGH SCHOOL, about 1.2 miles away. Within five miles of WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL, there are at least 8 other public schools. Of 9 schools in the immediate area with test results, WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL ranks 7th on average proficiency.

Locale data from NCES put WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL in a suburban area outside a principal city, within an urbanized area with a population of 250,000 or more (Suburb: Large).

Between 2020-21 and 2024-25, WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL had a net gain of 70 students, or 15%. The ratio of students to teachers went from 12.0:1 to 13.1:1 over the same years.

People can post here about open houses, carpools, and field trips and other school topics. Parents, students, alumni, and staff are welcome to post.

Suffolk County at a glance

View full county profile
Population
1,530,146
Census ACS
Median income
$130,686
Household, ACS
Bachelor's+
40%
Adults 25+
Poverty rate
4%
Below federal line
Schools in county
343
222,439 students

Quick facts

School name
WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL
District
THREE VILLAGE CENTRAL SCHOOL DISTRICT
Address
50 DEAN LN, STONY BROOK, NY 11790
Phone
(631) 730-4300
County
Suffolk County
Level
Elementary
Grade range
PK–06
Total enrollment
525
Teachers (FTE)
40
Student–teacher ratio
13.1:1
Free and reduced lunch
107 (20%)
Locale
21-Suburb: Large
NCES ID
362820003810
Charter school
No
Virtual school
No

Related schools

Other schools in THREE VILLAGE CENTRAL SCHOOL DISTRICT
Other schools in STONY BROOK
Nearby schools

Frequently asked questions

About WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL
How large is WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL?
WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL enrolls approximately 525 students in grades PK-06.
What grades does WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL serve?
WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL serves grades PK-06.
What is the student-teacher ratio at WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL?
The student-to-teacher ratio at WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL is approximately 13.1:1 (40 FTE teachers).
What is the racial breakdown of students at WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL?
At WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL, the student body is approximately 55% White, 14% Hispanic, 1% Black, 24% Asian, 5% Two or more.
Is WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL public or private?
WILLIAM SIDNEY MOUNT ELEMENTARY SCHOOL is a public K-12 school, overseen by THREE VILLAGE CENTRAL SCHOOL DISTRICT.
Data sourceSchool profile facts are sourced from the NCES. Community content is posted by allk12 members.
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