#1 Largest Private Schools in Suffolk County, NY
St. Anthony's High School
Parish school · Grades 9–12
2,435 students
Huntington Station, NY
B+Overall grade2,435 students19 students per teacher
2026 lists
Largest Private Schools in Suffolk County, NY
The private schools in Suffolk County, NY with the most students. Top 38 of 38 schools.
#2 Largest Private Schools in Suffolk County, NY
St. John the Baptist Diocesan High School
Diocesan school · Grades 9–12
969 students
West Islip, NY
AOverall grade969 students15 students per teacher
#3 Largest Private Schools in Suffolk County, NY
St. Patrick's School
Parish school · Grades Pre-K–8
445 students
Huntington, NY
A-Overall grade445 students11 students per teacher
#4 Largest Private Schools in Suffolk County, NY
The Stony Brook School
Christian school (nondenominational) · Grades 7–12
442 students
Stony Brook, NY
B+Overall grade442 students10 students per teacher
#5 Largest Private Schools in Suffolk County, NY
St. Patrick School
Diocesan school · Grades Pre-K–8
395 students
Bay Shore, NY
A-Overall grade395 students15 students per teacher
#6 Largest Private Schools in Suffolk County, NY
Smithtown Christian School
Christian school (nondenominational) · Grades K–12
385 students
Smithtown, NY
B-Overall grade385 students10 students per teacher
#7 Largest Private Schools in Suffolk County, NY
Our Lady of Guadalupe Catholic School
Diocesan school · Grades Pre-K–8
380 students
Deer Park, NY
A+Overall grade380 students12 students per teacher
#8 Largest Private Schools in Suffolk County, NY
St. Patrick Elementary School
Diocesan school · Grades Pre-K–8
379 students
Smithtown, NY
BOverall grade379 students15 students per teacher
#9 Largest Private Schools in Suffolk County, NY
St. Mary School
Parish school · Grades K–8
331 students
East Islip, NY
BOverall grade331 students16 students per teacher
#10 Largest Private Schools in Suffolk County, NY
Our Lady of the Hamptons Regional Catholic School
Parish school · Grades Pre-K–8
291 students
Southampton, NY
A+Overall grade291 students11 students per teacher
#11 Largest Private Schools in Suffolk County, NY
Ross School
Independent school · Grades Pre-K–12
286 students
East Hampton, NY
A+Overall grade286 students5 students per teacher
#12 Largest Private Schools in Suffolk County, NY
MDQ Academy
Islamic school · Grades Pre-K–12
276 students
Brentwood, NY
AOverall grade276 students9 students per teacher
#13 Largest Private Schools in Suffolk County, NY
Trinity Regional School-East Northport Campus
Diocesan school · Grades Pre-K–8
253 students
East Northport, NY
A-Overall grade253 students12 students per teacher
#14 Largest Private Schools in Suffolk County, NY
Holy Angels Regional School
Diocesan school · Grades Pre-K–8
191 students
Patchogue, NY
B+Overall grade191 students12 students per teacher
#15 Largest Private Schools in Suffolk County, NY
St. John Paul II Regional School
Diocesan school · Grades Pre-K–8
147 students
Riverhead, NY
AOverall grade147 students7 students per teacher
#16 Largest Private Schools in Suffolk County, NY
Long Island School for the Gifted
Independent school · Grades K–9
133 students
Huntington Station, NY
A+Overall grade133 students6 students per teacher
#17 Largest Private Schools in Suffolk County, NY
SS Philip & James School
Diocesan school · Grades Pre-K–8
126 students
Saint James, NY
AOverall grade126 students10 students per teacher
#18 Largest Private Schools in Suffolk County, NY
Developmental Disabilities Institute Huntington
Special education school · Ungraded
123 students
Huntington, NY
BOverall grade123 students8 students per teacher
#19 Largest Private Schools in Suffolk County, NY
Harbor Country Day School
Independent school · Grades Pre-K–8
117 students
Saint James, NY
A-Overall grade117 students6 students per teacher
#20 Largest Private Schools in Suffolk County, NY
The Knox School
Independent school · Grades 6–12
112 students
Saint James, NY
B+Overall grade112 students24 students per teacher
#21 Largest Private Schools in Suffolk County, NY
Developmental Disabilities Institute
Special education school · Ungraded
101 students
Smithtown, NY
BOverall grade101 students7 students per teacher
#22 Largest Private Schools in Suffolk County, NY
Our Savior New American School
Lutheran (Missouri Synod) school · Grades Pre-K–12
99 students
Centereach, NY
A+Overall grade99 students4 students per teacher
#23 Largest Private Schools in Suffolk County, NY
Nysarc INC-Suffolk Chapter
Special education school · Pre-K only
90 students
Bohemia, NY
B+Overall grade90 students10 students per teacher
#24 Largest Private Schools in Suffolk County, NY
Ivy League School
Independent school · Grades Pre-K–8
84 students
Smithtown, NY
B+Overall grade84 students6 students per teacher
From official public records, updated October 2026.