| Chapter | Charter date | Institution | Location | State or province | Status | References |
| | | Agnes Irwin School | Rosemont, Pennsylvania | PA | Active | |
| | | The Albany Academy | Albany, New York | NY | Active | |
| | | Albany Academy for Girls | Albany, New York | NY | Active | |
| | | Albuquerque Academy | Albuquerque, New Mexico | NM | Active | |
| | | All Saints Episcopal School | Tyler, Texas | TX | Active | |
| | | Allendale Columbia School | Rochester, New York | NY | Active | |
| | | American School of Madrid | Pozuelo de Alarcón, Madrid, Spain | | Active | |
| | | American School of Paris | Saint-Cloud, Île-de-France, France | | Active | |
| | | Anderson High School | Cincinnati, Ohio | OH | Active | |
| | | Arendell Parrott Academy | Kinston, North Carolina | NC | Active | |
| | | Athens Academy | Athens, Georgia | GA | Active | |
| | | Augusta Preparatory Day School | Martinez, Georgia | GA | Active | |
| | | Asheville School | Asheville, North Carolina | NC | Active | |
| | | Avon Old Farms School | Avon, Connecticut | CT | Active | |
| | | Bancroft School | Worcester, Massachusetts | MA | Active | |
| | | The Barstow School | Kansas City, Missouri | MO | Active | |
| | | Battle Ground Academy | Franklin, Tennessee | TN | Active | |
| | | Baylor School | Chattanooga, Tennessee | TN | Active | |
| | | Beaver Country Day School | Chestnut Hill, Massachusetts | MA | Active | |
| | | Belmont Hill School | Belmont, Massachusetts | MA | Active | |
| | | The Benjamin School | Palm Beach County, Florida | FL | Active | |
| | | Berkeley Carroll School | Park Slope, New York City, New York | NY | Active | |
| | | Berkeley Preparatory School | Tampa, Florida | FL | Active | |
| | | Berkshire School | Sheffield, Massachusetts | MA | Active | |
| | | Berwick Academy | South Berwick, Maine | ME | Active | |
| | | Bexley High School | Bexley, Ohio | OH | Active | |
| | | Birch Wathen Lenox School | Manhattan, New York City, New York | NY | Active | |
| | | The Bishop's School | La Jolla, California | CA | Active | |
| | | Blair Academy | Blairstown, New Jersey | NJ | Active | |
| | | The Blake School | Hopkins, Minnesota | MN | Active | |
| | | The Branson School | Ross, California | CA | Active | |
| | | Brentwood School | Los Angeles, California | CA | Active | |
| | | Breck School | Golden Valley, Minnesota | MN | Active | |
| | | Brookfield Academy | Brookfield, Wisconsin | WI | Active | |
| | before December 1908 | Brooklyn Collegiate and Polytechnic Institute | Brooklyn, New York | NY | Inactive | [4][a][b] |
| | | Brooks School | North Andover, Massachusetts | MA | Active | |
| | | Brookstone School | Columbus, Georgia | GA | Active | |
| | | Brunswick School | Greenwich, Connecticut | CT | Active | |
| | | Bryn Mawr School | Baltimore, Maryland | MD | Active | |
| | | Buckingham Browne & Nichols School | Cambridge, Massachusetts | MA | Active | |
| | | Buffalo Seminary | Buffalo, New York | NY | Active | |
| | | Byram Hills High School | Armonk, New York | NY | Active | |
| | | Campbell Hall School | Studio City, Los Angeles, California | CA | Active | |
| | | Cannon School | Concord, North Carolina | NC | Active | |
| | | Canterbury School | Fort Wayne, Indiana | IN | Active | |
| | | Canterbury School | St. Petersburg, Florida | FL | Active | |
| | | Cape Cod Academy | Osterville, Massachusetts | MA | Active | |
| | | Cape Henry Collegiate School | Virginia Beach, Virginia | VA | Active | |
| | 2019 | Carrollwood Day School | Tampa, Florida | FL | Active | [5] |
| | | Casady School | Oklahoma City, Oklahoma | OK | Active | |
| | | Castilleja School | Palo Alto, California | CA | Active | |
| | | Cate School | Carpinteria, California | CA | Active | |
| | before December 1908 | Centenary Collegiate Institute | Hackettstown, New Jersey | NJ | Inactive | [4][c][b] |
| | | Chadwick School | Palos Verdes Peninsula, California | CA | Active | |
| | | Chagrin Falls High School | Chagrin Falls, Ohio | OH | Active | |
| | | Charles Wright Academy | University Place, Washington | WA | Active | |
| | | Charlotte Country Day School | Charlotte, North Carolina | NC | Active | |
| | | Charlotte Latin School | Charlotte, North Carolina | NC | Active | |
| | | Chase Collegiate School | Waterbury, Connecticut | CT | Active | |
| | | Chatham Hall | Chatham, Virginia | VA | Active | |
| | | Cherry Hill High School East | Cherry Hill, New Jersey | NJ | Active | |
| | | Choate Rosemary Hall | Wallingford, Connecticut | CT | Active | |
| | | Christ Church Episcopal School | Greenville, South Carolina | SC | Active | |
| | | Cincinnati Country Day School | Indian Hill, Ohio | OH | Active | |
| | | Cistercian Preparatory School | Irving, Texas | TX | Active | |
| | | Classical High School | Providence, Rhode Island | RH | Active | |
| | | The College Preparatory School | Oakland, California | CA | Active | |
| | | Collegiate School | Manhattan, New York | NY | Active | |
| | | Collegiate School | Richmond, Virginia | VA | Active | |
| | | Collierville High School | Collierville, Tennessee | TN | Active | |
| | | Columbus Academy | Gahanna, Ohio | OH | Active | |
| | | Columbus School for Girls | Bexley, Ohio | OH | Active | |
| | | Columbus Torah Academy | Columbus, Ohio | OH | Active | |
| | | Community School of Naples | Naples, Florida | FL | Active | |
| | | The Covenant School | Charlottesville, Virginia | VA | Active | |
| | | Cranbrook Schools | Bloomfield Hills, Michigan | MI | Active | |
| | | Crystal Springs Uplands School | Hillsborough, California | CA | Active | |
| | | Culver Academies | Culver, Indiana | IN | Active | |
| | | Cushing Academy | Ashburnham, Massachusetts | MA | Active | |
| | | Dana Hall School | Wellesley, Massachusetts | MA | Active | |
| | | Darlington School | Rome, Georgia | GA | Active | |
| | | Deerfield Academy | Deerfield, Massachusetts | MA | Active | |
| | | Detroit Country Day School | Beverly Hills, Michigan | MI | Active | |
| | | Doane Academy | Burlington, New Jersey | NJ | Active | |
| | | Durham Academy | Durham, North Carolina | NC | Active | |
| | | Dwight-Englewood School | Englewood, New Jersey | NJ | Active | |
| | | Edgemont High School | Edgemont, New York | NY | Active | |
| | | Elgin Academy | Elgin, Illinois | IL | Active | [d] |
| | | The Ellis School | Pittsburgh, Pennsylvania | PA | Active | |
| | | Emma Willard School | Troy, New York | NY | Inactive | |
| | | Episcopal Academy | Newtown Square, Pennsylvania | PA | Active | |
| | | Episcopal Collegiate School | Little Rock, Arkansas | AR | Active | |
| | | Episcopal High School | Alexandria, Virginia | VA | Active | |
| | | Episcopal School of Dallas | Dallas, Texas | TX | Active | |
| | | Episcopal School of Jacksonville | Jacksonville, Florida | FL | Active | |
| | | Ethel Walker School | Simsbury, Connecticut | CT | Active | |
| | before December 1908 | Evanston Academy | Evanston, Illinois | IL | Inactive | [4][6][e][b] |
| | | Father Ryan High School | Nashville, Tennessee | TN | Active | |
| | | Flint Hill School | Oakton, Virginia | VA | Active | |
| | | Flintridge Preparatory School | La Cañada Flintridge, California | CA | Active | |
| | | Forsyth Country Day School | Lewisville, North Carolina | NC | Active | |
| | | Fort Worth Country Day School | Fort Worth, Texas | TX | Active | [7] |
| | | Fountain Valley School of Colorado | Colorado Springs, Colorado | CO | Active | |
| | | Foxcroft School | Middleburg, Virginia | VA | Active | |
| | | Francis Parker School | San Diego, California | CA | Active | |
| | | Franklin Road Academy | Nashville, Tennessee | TN | Active | |
| | | Friends Academy | Glen Cove, New York | NY | Active | |
| | | Friends' Central School | Wynnewood, Pennsylvania | PA | Active | |
| | | Friends School of Baltimore | Baltimore, Maryland | MD | Active | |
| | | Fuqua School | Farmville, Virginia | VA | Active | |
| | | Garrison Forest School | Owings Mills, Maryland | MD | Active | |
| | | Georgetown Visitation Preparatory School | Washington, D.C. | DC | Active | |
| | | Germantown Academy | Fort Washington, Pennsylvania | PA | Active | |
| | | Gill St. Bernard's School | Somerset County, New Jersey | NJ | Active | |
| | | Gilman School | Baltimore, Maryland | MD | Active | |
| | | Gilmour Academy | Gates Mills, Ohio | OH | Active | |
| | | Girls Preparatory School | Chattanooga, Tennessee | TN | Active | |
| | | Glenbrook South High School | Glenview, Illinois | IL | Active | |
| | | Glenelg Country School | Howard County, Maryland | MD | Active | |
| | | Gould Academy | Bethel, Maine | ME | Active | |
| | | The Governor's Academy | Byfield, Massachusetts | MA | Active | |
| | | Granville High School | Granville, Ohio | OH | Active | |
| | | Greenhill School | Addison, Texas | TX | Active | |
| | | Greenhills School | Ann Arbor, Michigan | MI | Active | |
| | | Greens Farms Academy | Greens Farms, Connecticut | CT | Active | |
| | | Greensboro Day School | Greensboro, North Carolina | NC | Active | |
| | | Greenwich Academy | Greenwich, Connecticut | CT | Active | |
| | | Gulliver Preparatory School | Kendall, Florida | FL | Active | |
| | | The Frederick Gunn School | Washington, Connecticut | CT | Active | |
| | | Hackley School | Tarrytown, New York | NY | Active | |
| | | Hall High School | Little Rock, Arkansas | AR | Active | |
| | | Hamden Hall Country Day School | Hamden, Connecticut | CT | Active | |
| | | Hammond School | Columbia, South Carolina | SC | Active | |
| | | Hampton Roads Academy | Newport News, Virginia | VA | Active | |
| | | Harpeth Hall School | Nashville, Tennessee | TN | Active | |
| | | Harvard-Westlake School | Los Angeles, California | CA | Active | |
| | | Hathaway Brown School | Shaker Heights, Ohio | OH | Active | |
| | 1930 | Haverford School | Haverford, Pennsylvania | PA | Active | |
| | | Hawaii Preparatory Academy | Kamuela, Hawaii | HI | Active | |
| | | Hawken School | Gates Mills, Ohio | OH | Active | |
| | | Head-Royce School | Oakland, California | CA | Active | |
| | | Heathwood Hall Episcopal School | Columbia, South Carolina | SC | Active | |
| | | Hebron Academy | Hebron, Maine | ME | Active | |
| | | Heritage Hall School | Oklahoma City, Oklahoma | OK | Active | |
| | | Hewitt School | New York City, New York | NY | Active | |
| | | Highlands High School | Fort Thomas, Kentucky | KY | Active | |
| | | The Hill School | Pottstown, Pennsylvania | PA | Active | |
| | | Hockaday School | Dallas, Texas | TX | Active | |
| | | Holderness School | Holderness, New Hampshire | NH | Active | |
| | | Holland Hall School | Tulsa, Oklahoma | OK | Active | |
| | | Holton-Arms School | Bethesda, Maryland | MD | Active | |
| | | Holy Innocents' Episcopal School | Sandy Springs, Georgia | GA | Active | |
| | | Hopkins School | New Haven, Connecticut | CT | Active | |
| | | Horace Mann School | Bronx, New York City, New York | NY | Active | |
| | | Hotchkiss School | Lakeville, Connecticut | CT | Active | |
| | | Hun School of Princeton | Princeton, New Jersey | NJ | Active | |
| | | Hutchison School | Memphis, Tennessee | TN | Active | |
| | | International School Manila | Taguig, Metro Manila, Philippines | MM | Active | |
| | | Iolani School | Honolulu, Hawaii | HI | Active | |
| | | Irvington High School | Irvington, New York | NY | Active | |
| | | Isidore Newman School | New Orleans, Louisiana | LA | Active | |
| | | Jackson Academy | Jackson, Mississippi | MS | Active | |
| | | Jackson Preparatory School | Flowood, Mississippi | MS | Active | |
| | | The John Cooper School | The Woodlands, Texas | TX | Active | |
| | | Kent Denver School | Cherry Hills Village, Colorado | CO | Active | |
| | | Kent Place School | Summit, New Jersey | NJ | Active | |
| | 1930 | Kent School | Kent, Connecticut | CT | Active | |
| | | Kents Hill School | Kents Hill, Maine | ME | Active | |
| | | Kentucky Country Day School | Louisville, Kentucky | KY | Active | |
| | | Kimball Union Academy | Meriden, New Hampshire | NH | Active | |
| | | King School | Stamford, Connecticut | CT | Active | |
| | | Kingswood Oxford School | West Hartford, Connecticut | CT | Active | |
| | | The Kinkaid School | Piney Point Village, Texas | TX | Active | |
| | | The Kiski School | Saltsburg, Pennsylvania | PA | Active | |
| | | La Jolla Country Day School | University City, San Diego, California | CA | Active | |
| | | La Jolla High School | San Diego, California | CA | Active | |
| | | Laguna Blanca School | Santa Barbara and Montecito, California | CA | Active | |
| | | Lake Forest Academy | Lake Forest, Illinois | IL | Active | |
| | | Lake Forest High School | Lake Forest, Illinois | IL | Active | |
| | | Lake Highland Preparatory School | Orlando, Florida | FL | Active | |
| | | Landon School | Bethesda, Maryland | MD | Active | |
| | | Latin School of Chicago | Chicago, Illinois | IL | Active | |
| | | Laurel School | Shaker Heights, Ohio | OH | Active | |
| | | Lausanne Collegiate School | Memphis, Tennessee | TN | Active | [8] |
| | | Lawrence Academy at Groton | Groton, Massachusetts | MA | Active | |
| | | Lawrence Woodmere Academy | Woodmere, New York | NY | Active | |
| | | Lawrenceville School | Lawrenceville, New Jersey | NJ | Active | |
| | | Lincoln-Sudbury Regional High School | Sudbury, Massachusetts | MA | Active | |
| | | Little Rock Central High School | Little Rock, Arkansas | AR | Active | |
| | | Loomis Chaffee School | Windsor, Connecticut | CT | Active | |
| | | Louisville Collegiate School | Louisville, Kentucky | KY | Active | |
| | | Lovett School | Atlanta, Georgia | GA | Active | |
| | | MacDuffie School | Granby, Massachusetts | MA | Active | |
| | | Maclay School | Tallahassee, Florida | FL | Active | |
| | | Mariemont High School | Mariemont, Ohio | OH | Active | |
| | | Maret School | Washington, D.C. | DC | Active | |
| | | Marin Academy | San Rafael, California | CA | Active | |
| | | Marlborough School | Los Angeles, California | CA | Active | |
| | | Mary Institute and St. Louis Country Day School | Ladue, Missouri | MO | Active | [9] |
| | | Marymount High School | Los Angeles, California | CA | Active | |
| | | Masters School | Dobbs Ferry, New York | NY | Active | |
| | | Maumee Valley Country Day School | Toledo, Ohio | OH | Active | |
| | | The McCallie School | Chattanooga, Tennessee | TN | Active | |
| | | McDonogh School | Owings Mills, Maryland | MD | Active | |
| | | The Meadows School | Las Vegas, Nevada | NV | Active | |
| | | Memphis University School | Memphis, Tennessee | TN | Active | |
| | 1930 | Mercersburg Academy | Mercersburg, Pennsylvania | PA | Active | |
| | | Metairie Park Country Day School | Metairie, Louisiana | LA | Active | |
| | | Millbrook School | Stanford, New York | NY | Active | |
| | | Milton Academy | Milton, Massachusetts | MA | Active | |
| | | Miss Hall's School | Pittsfield, Massachusetts | MA | Active | |
| | | Miss Porter's School | Farmington, Connecticut | CT | Active | |
| | | Montclair Kimberley Academy | Montclair, New Jersey | NJ | Active | |
| | | Montgomery Academy | Montgomery, Alabama | AL | Active | |
| | | Moorestown Friends School | Moorestown, New Jersey | NJ | Active | |
| | | Montgomery Bell Academy | Nashville, Tennessee | TN | Active | |
| | | Montverde Academy | Montverde, Florida | FL | Active | |
| | | Moravian Academy | Bethlehem and Allentown, Pennsylvania | PA | Active | |
| | | Morgan Park Academy | Chicago, Illinois | IL | Active | |
| | | Morristown–Beard School | Morristown, New Jersey | NJ | Active | |
| | 1930 | Moses Brown School | Providence, Rhode Island | RH | Active | [10] |
| | | Mounds Park Academy | Maplewood, Minnesota | MN | Active | |
| | | Mount de Sales Academy | Macon, Georgia | GA | Active | |
| | | Mt. Lebanon High School | Mt. Lebanon, Pennsylvania | PA | Active | |
| | | Mount St. Mary Academy | Watchung, New Jersey | NJ | Active | |
| | | National Cathedral School | Washington, D.C. | DC | Active | |
| | | New Hampton School | New Hampton, New Hampshire | NH | Active | |
| | | Newark Academy | Livingston, New Jersey | NJ | Active | |
| | | Newton South High School | Newton, Massachusetts | MA | Active | |
| | | Nichols School | Buffalo, New York | NY | Active | |
| | | Nightingale-Bamford School | Manhattan, New York | NY | Active | |
| | | Noble and Greenough School | Dedham, Massachusetts | MA | Active | |
| | | Norfolk Academy | Norfolk, Virginia | VA | Active | |
| | | North Cross School | Roanoke, Virginia | VA | Active | |
| | | North Yarmouth Academy | Yarmouth, Maine | ME | Active | |
| | | Northfield Mount Hermon School | Gill, Massachusetts | MA | Active | |
| | | Northwood School | Lake Placid, New York | NY | Active | |
| | | Notre Dame Preparatory School | Towson, Maryland | MD | Active | |
| | | Oak Hall School | Gainesville, Florida | FL | Active | |
| | | Oak Knoll School of the Holy Child | Summit, New Jersey | NJ | Active | |
| | | Oak Park and River Forest High School | Oak Park, Illinois | IL | Active | |
| | | The O'Neal School | Southern Pines, North Carolina | NC | Active | |
| Newman | 2016 | Oratory Preparatory School | Summit, New Jersey | NJ | Active | [11] |
| | | Out-of-Door Academy | Sarasota, Florida | FL | Active | |
| | | Pace Academy | Atlanta, Georgia | GA | Active | |
| | | Pacific Ridge School | Carlsbad, California | CA | Active | |
| | | Packer Collegiate Institute | Brooklyn, New York City, New York | NY | Active | |
| | | Parish Episcopal School | Dallas, Texas | TX | Active | |
| | | Park Tudor School | Indianapolis, Indiana | IN | Active | |
| | | Peddie School | Hightstown, New Jersey | NJ | Active | |
| | | The Pembroke Hill School | Kansas City, Missouri | MO | Active | |
| | | The Pennington School | Pennington, New Jersey | NJ | Active | [12] |
| | | Perkiomen School | Pennsburg, Pennsylvania | PA | Active | |
| | before December 1908 | Phillips Academy | Andover, Massachusetts | MA | Active | [4][b] |
| | before December 1908 | Phillips Exeter Academy | Exeter, New Hampshire | NH | Active | [4][b] |
| | | Pine Crest School | Fort Lauderdale and Boca Raton, Florida | FL | Active | |
| | | Pingree School | South Hamilton, Massachusetts | MA | Active | |
| | | Pingry School | Short Hills, New Jersey | NJ | Active | |
| | | Poly Prep Country Day School | Dyker Heights, Brooklyn, New York City, New York | NY | Active | |
| | | Polytechnic School | Pasadena, California | CA | Active | |
| | | Pomfret School | Pomfret, Connecticut | CT | Active | |
| | | Portledge School | Matinecock, New York | NY | Active | |
| | | Porter-Gaud School | Charleston, South Carolina | SC | Active | |
| | | Portsmouth Abbey School | Portsmouth, Rhode Island | RH | Active | |
| | | The Prairie School | Wind Point, Wisconsin | WI | Active | |
| | | Princeton Day School | Princeton, New Jersey | NJ | Active | |
| | | Principia School | Town and Country, Missouri | MO | Active | |
| | | Providence Country Day School | East Providence, Rhode Island | RH | Active | |
| | | Providence Day School | Charlotte, North Carolina | NC | Active | |
| | | Pulaski Academy | Little Rock, Arkansas | AR | Active | |
| | | Rabun Gap-Nacoochee School | Rabun Gap, Georgia | GA | Active | |
| | | Randolph School | Huntsville, Alabama | AL | Active | |
| | | Ranney School | Tinton Falls, New Jersey | NJ | Active | |
| | | Ransom Everglades School | Coconut Grove, Florida | FL | Active | |
| | | Ravenscroft School | Raleigh, North Carolina | NC | Actove | |
| | | Rivers School | Weston, Massachusetts | MA | Active | |
| | 1962 | Roland Park Country School | Baltimore, Maryland | MD | Active | [13] |
| | | Roxbury Latin School | West Roxbury, Massachusetts | MA | Active | |
| | | Rutgers Preparatory School | Franklin Township, New Jersey | NJ | Active | |
| | | Sacramento Country Day School | Arden-Arcade, California | CA | Active | |
| | | Sacred Heart Greenwich | Greenwich, Connecticut | CT | Active | [f] |
| | | Saddle River Day School | Saddle River, New Jersey | NJ | Active | |
| | | St. Albans School | Washington, D.C. | DC | Active | |
| | | St. Andrew's Episcopal School | Potomac, Maryland | MD | Active | |
| | | St. Andrew's Episcopal School | Ridgeland, Mississippi | MS | Active | |
| | | Saint Andrew's School | Boca Raton, Florida | FL | Active | |
| | | St. Andrew's-Sewanee School | Sewanee, Tennessee | TN | Active | |
| | | St. Anne's-Belfield School | Charlottesville, Virginia | VA | Active | |
| | | St. Catherine's School | Richmond, Virginia | VA | Active | |
| | | Saint Edward's School | Vero Beach, Florida | FL | Active | |
| | | St. George's Independent School | Memphis, Collierville, and Germantown, Tennessee | TN | Active | |
| | | St. George's School | Middletown, Rhode Island | RH | Active | |
| | | Saint George's School | Spokane, Washington | WA | Active | |
| | | Saint James School | Hagerstown, Maryland | MD | Active | |
| | | St. Johns Country Day School | Orange Park, Florida | FL | Active | |
| | | Saint John's School | San Juan, Puerto Rico | PR | Active | |
| | | St. John's School | Houston, Texas | TX | Active | |
| | | St. Luke's School | New Canaan, Connecticut | CT | Active | |
| | | St. Margaret's Episcopal School | San Juan Capistrano, California | CA | Active | |
| | | St. Mark's School | Southborough, Massachusetts | MA | Active | |
| | | St. Mark's School of Texas | Dallas, Texas | TX | Active | |
| | | St. Martin's Episcopal School | Metairie, Louisiana | LA | Active | |
| | | St. Mary's Episcopal School | Memphis, Tennessee | TN | Active | |
| | | Saint Mary's Hall | San Antonio, Texas | TX | Active | |
| | | St. Mary's School | Medford, Oregon | OR | Active | |
| | | St. Paul Academy and Summit School | Saint Paul, Minnesota | MN | Active | |
| | | St. Paul's School | Concord, New Hampshire | NH | Active | |
| | | St. Paul's School for Boys | Brooklandville, Maryland | MD | Active | |
| | | St. Paul's School for Girls | Brooklandville, Maryland | MD | Active | |
| | | Saint Sebastian's School | Needham, Massachusetts | MA | Active | |
| | | St. Stephen's & St. Agnes School | Alexandria, Virginia | VA | Active | |
| | | St. Stephen's Episcopal School | Austin, Texas | TX | Active | |
| | | Saint Stephen's Episcopal School | Bradenton, Florida | FL | Active | [14] |
| | | St. Timothy's School | Stevenson, Maryland | MD | Active | |
| | | Salisbury School | Salisbury, Connecticut | CT | Active | |
| | | Sanford School | Hockessin, Delaware | DE | Active | |
| | | Santa Catalina School | Monterey, California | CA | Active | |
| | | Santa Fe Preparatory School | Santa Fe, New Mexico | NM | Active | |
| | | Savannah Country Day School | Savannah, Georgia | GA | Active | |
| | | Seabury Hall | Makawao, Hawaii | HI | Active | |
| | | Selwyn House School | Westmount, Quebec, Canada | QC | Active | |
| | | Seven Hills School | Cincinnati, Ohio | OH | Active | [15] |
| | | Severn School | Severna Park, Maryland | MD | Active | |
| | | Shady Side Academy | Pittsburgh, Pennsylvania | PA | Active | |
| | | Shattuck-Saint Mary's | Faribault, Minnesota | MN | Active | |
| | | Shorecrest Preparatory School | St. Petersburg, Florida | FL | Active | |
| | | Sierra Canyon School | Los Angeles, California | CA | Active | |
| | | South Kent School | South Kent, Connecticut | CT | Active | |
| | | Spartanburg Day School | Spartanburg, South Carolina | SC | Active | |
| | | Springside Chestnut Hill Academy | Philadelphia, Pennsylvania | PA | Active | |
| | | Stevenson School | Pebble Beach, California | CA | Active | |
| | | Stone Ridge School of the Sacred Heart | Bethesda, Maryland | MD | Active | [16] |
| | 1930 | The Stony Brook School | Stony Brook, New York | NY | Active | |
| | | Storm King School | Cornwall-on-Hudson, New York | NY | Active | |
| | | Suffield Academy | Suffield, Connecticut | CT | Active | |
| | | Tabor Academy | Marion, Massachusetts | MA | Active | |
| | | Taft School | Watertown, Connecticut | CT | Active | [17] |
| | | Tampa Preparatory School | Tampa, Florida | FL | Active | |
| | | Tatnall School | Wilmington, Delaware | DE | Active | |
| | | TASIS England | Thorpe, Surrey, England | | Active | |
| | | TASIS Switzerland | Montagnola, Collina d'Oro, Switzerland | | Active | |
| | | The Thacher School | Ojai, California | CA | Active | |
| | | Thayer Academy | Braintree, Massachusetts | MA | Active | |
| | | Tilton School | Tilton, New Hampshire | NH | Active | |
| | 1906 | Tome School | Port Deposit, Maryland | MD | Inacitve | [4][g] |
| | | Tower Hill School | Wilmington, Delaware | DE | Active | |
| | | Trinity Preparatory School | Winter Park, Florida | FL | Active | |
| | | Trinity School | New York City, New York | NY | Active | |
| | | Trinity-Pawling School | Dutchess County, New York | NY | Active | |
| | | Tupelo High School | Tupelo, Mississippi | MS | Active | |
| | | UMS-Wright Preparatory School | Mobile, Alabama | AL | Active | |
| | | University High School | Carmel, Indiana | IN | Active | |
| | | University Lake School | Delafield, Wisconsin | WI | Active | |
| | | University Liggett School | Grosse Pointe Woods, Michigan | MI | Active | |
| | | University School | Shaker Heights and Hunting Valley, Ohio | OH | Active | |
| | | University School of Milwaukee | Milwaukee, Wisconsin | WI | Active | [18] |
| | | University School of Nashville | Nashville, Tennessee | TN | Active | |
| | | Upper Arlington High School | Upper Arlington, Ohio | OH | Active | [19] |
| | | Vermont Academy | Saxtons River, Vermont | VT | Active | |
| | | Viewpoint School | Calabasas, California | CA | Active | |
| | | Virginia Episcopal School | Lynchburg, Virginia | VA | Active | |
| | | Walnut Hills High School | Cincinnati, Ohio | OH | Active | |
| | | Walnut Hill School | Natick, Massachusetts | MA | Active | |
| | | Wardlaw-Hartridge School | Edison, New Jersey | NJ | Active | |
| | | Waterford School | Sandy, Utah | UT | Active | |
| | | Watertown High School | Watertown, Massachusetts | MA | Active | |
| | June 14, 1910 | Wayland Academy | Beaver Dam, Wisconsin | WI | Active | [4][h] |
| | | Waynflete School | Portland, Maine | ME | Active | |
| | | The Webb School | Bell Buckle, Tennessee | TN | Active | |
| | | Webb School of Knoxville | Knoxville, Tennessee | TN | Active | |
| | | The Webb Schools | Claremont, California | CA | Active | |
| | | The Wellington School | Upper Arlington, Ohio | OH | Active | |
| | | Western Reserve Academy | Hudson, Ohio | OH | Active | |
| | | The Westminster Schools | Atlanta, Georgia | GA | Active | |
| | | Westridge School | Pasadena, California | CA | Active | |
| | | Wheeler School | Providence, Rhode Island | RH | Active | |
| | | Wichita Collegiate School | Wichita, Kansas | KS | Active | |
| | | Wilbraham & Monson Academy | Wilbraham, Massachusetts | MA | Active | |
| | before December 1908 | William Penn Charter School | Philadelphia, Pennsylvania | PA | Active | [20][4][b] |
| | | The Williams School | New London, Connecticut | CT | Active | |
| | | Williston Northampton School | Easthampton, Massachusetts | MA | Active | |
| | | Winchester Thurston School | Pittsburgh, Pennsylvania | PA | Active | |
| | | Windward School | Los Angeles, California | CA | Active | |
| | | Withrow High School | Cincinnati, Ohio | OH | Active | |
| | | Woodberry Forest School | Woodberry Forest, Virginia | VA | Active | |
| | | Wooster School | Danbury, Connecticut | CT | Active | |
| | | Worcester Academy | Worcester, Massachusetts | MA | Active | |
| | | Worcester Preparatory School | Berlin, Maryland | MD | Active | |
| | | Wyoming Seminary | Kingston, Pennsylvania | PA | Active | |
| | | York Country Day School | York, Pennsylvania | PA | Active | |