The Independent School League or ISL is a group of seventeen preparatory schools located in the Washington metropolitan area of the United States that compete with each other athletically. All competitors in the ISL are girls, but not all schools are "all-girls" schools. The league is broken into two divisions: A and AA. The schools which compete in each division vary by sport.
Member schools
| School | Location | Colors | Team name | Established | Enrollment | Joined |
|---|---|---|---|---|---|---|
| Bullis School | Potomac, Maryland | Bulldogs | 1930 | 750 | - | |
| Connelly School of the Holy Child | Potomac, Maryland | Tigers | 1961 | - | - | |
| Episcopal High School | Alexandria, Virginia | Maroon | 1839 | 450 | - | |
| Flint Hill School | Oakton, Virginia | Huskies | 1956 | 1,100 | - | |
| Georgetown Day School | Washington, D.C. | Mighty Hoppers | 1945 | 1,050 | - | |
| Georgetown Visitation Preparatory School | Washington, D.C. | Cubs | 1799 | 475 | - | |
| Holton-Arms School | Bethesda, Maryland | Panthers | 1901 | 650 | - | |
| The Madeira School | McLean, Virginia | Snails | 1906 | 300 | - | |
| Maret School | Washington, D.C. | Frogs | 1911 | 625 | - | |
| Model Secondary School for the Deaf | Washington, D.C. | Eagles | 1969 | - | - | |
| National Cathedral School | Washington, D.C. | Eagles | 1900 | 575 | - | |
| The Potomac School | McLean, Virginia | Panthers | 1904 | 1,025 | - | |
| Sandy Spring Friends School | Sandy Spring, Maryland | Wildebeests | 1961 | 575 | - | |
| Sidwell Friends School | Washington, D.C. | Quakers | 1883 | 1,050 | - | |
| St. Andrew's Episcopal School | Potomac, Maryland | Lions | 1978 | 525 | - | |
| St. Stephen's & St. Agnes School | Alexandria, Virginia | Saints | 1924 | 1,125 | - | |
| Stone Ridge School of the Sacred Heart | Bethesda, Maryland | Gators | 1923 | 700 | - |