Members' Schools (current total 164)
| Seaford College | 2014 |
| Sebright | 1964 |
| Sedbergh | 1964 |
| Sevenoaks | 1965 |
| Sherborne | 1965 |
| Shrewsbury | 1963 |
| Solihull | 1962 |
| St. Albans | 2010 |
| St. Aloysius | 2010 |
| St. Bees | 1963 |
| St. Columba's | 2006 |
| St. Dunstan's | 1962 |
| St. Edward's Oxford | 1964 |
| St. Georges (Harpenden) | 1970 |
| St. Georges (Weybridge) | 1966 |
| St. John's Leatherhead | 2005 |
| St. Lawrence | 1962 |
| St. Paul's | 1963 |
| St. Peter's York | 1963 |
| Stamford | 1962 |
| Stewart's Melville | 2017 |
| Stockport | 1962 |
| Stonyhurst | 1963 |
| Stowe | 1963 |
| Strathallan | 1977 |
| Sutton Valence | 1962 |