| School | HMC Division | Membership | Location | Age Range |
| Sedbergh School | North East (UK) | British Isles | Sedbergh, United Kingdom | 13 - 18 |
| Sevenoaks School | South East (UK) | British Isles | Sevenoaks, United Kingdom | 11 - 18 |
| Sherborne School | South West (UK) | British Isles | Sherborne, United Kingdom | 13 - 18 |
| Sherborne School for Girls | South West (UK) | British Isles | Sherborne, United Kingdom | 11 - 18 |
| Shiplake College | South Central (UK) | British Isles | Oxon, United Kingdom | 11 - 18 |
| Shrewsbury International School Bangkok | International | International | Bangkok, Thailand | 2 - 18 |
| Shrewsbury School | West (UK) | British Isles | Shrewsbury, United Kingdom | 11 - 18 |
| Sidcot School | South West (UK) | British Isles | Winscombe, United Kingdom | 3 - 18 |
| Sir William Perkins’s School | London (UK) | British Isles | Chertsey, Surrey, United Kingdom | 11 - 18 |
| Solihull School | West (UK) | British Isles | Solihull, United Kingdom | 3 - 18 |
| South Hampstead High School | London (UK) | British Isles | Hampstead, London, United Kingdom | 4 - 18 |
| St Albans High School for Girls | London (UK) | British Isles | St Albans, United Kingdom | 4 - 18 |
| St Albans School | London (UK) | British Isles | St Albans, United Kingdom | 11 - 18 |
| St Aloysius’ College | Scottish (UK) | British Isles | Glasgow, United Kingdom | 3 - 18 |
| St Andrew’s Cathedral School | International | Associate (International) | Sydney, Australia | 3 - 18 |
| St Andrews Turi | International | International | Molo, Kenya | 3 - 18 |
| St Bede’s College | North West (UK) | British Isles | Manchester, United Kingdom | 3 - 18 |
| St Benedict’s School | London (UK) | British Isles | Ealing, London, United Kingdom | 3 - 18 |
| St Catherine’s British School | International | International | Athens, Greece | 3 - 18 |
| St Christopher’s School | International | International | Isa Town, Kingdom of Bahrain | 3 - 18 |
| St Columba’s College, Dublin | Irish | British Isles | Dublin, Republic of Ireland | 12 - 18 |
| St Columba’s College, St Albans | London (UK) | British Isles | St Albans, United Kingdom | 4 - 18 |
| St Columba’s School, Kilmacolm | Scottish (UK) | British Isles | Kilmacolm, United Kingdom | 3 - 18 |
| St Dunstan’s College | London (UK) | British Isles | Catford, London, United Kingdom | 3 - 18 |
| St Edmund’s College | London (UK) | British Isles | Ware, United Kingdom | 3 - 18 |
| St Edmund’s School, Canterbury | South East (UK) | British Isles | Canterbury, United Kingdom | 3 - 18 |
| St Edward’s School | South Central (UK) | British Isles | Oxford, United Kingdom | 13 - 18 |
| St George’s College | International | International | Quilmes, Argentina | 3 - 18 |
| St George’s College North | International | International | Buenos Aires, Argentina | 3 - 18 |
| St George’s College Weybridge | London (UK) | British Isles | Addlestone, United Kingdom | 11 - 18 |
| St George’s College, Zimbabwe | International | International | Harare, Zimbabwe | 13 - 18 |
| St George’s British International School, Rome | International | International | Rome, Italy | 3 - 18 |
| St Helen and St Katharine | South Central (UK) | British Isles | Abingdon, United Kingdom | 9 - 18 |
| St Helens’s School | London (UK) | British Isles | Northwood, United Kingdom | 3 - 18 |
| St John’s School | South East (UK) | British Isles | Leatherhead, United Kingdom | 11 - 18 |
| St Julian’s School | International | International | Carcavelos, Portugal | 3 - 18 |
Sedbergh School
Age range
13 - 18
Location
Station Road, Sedbergh, Cumbria, LA10 5HG, United Kingdom
Head’s name
Dan Harrison
Sevenoaks School
Age range
11 - 18
Location
High Street, Sevenoaks, Kent, TN13 1HU, United Kingdom
Head’s name
Jesse Elzinga
Sherborne School
Age range
13 - 18
Location
Abbey Road, Sherborne, Dorset, DT9 3AP, United Kingdom
Head’s name
Simon Heard
Sherborne School for Girls
Age range
11 - 18
Location
Bradford Road, Sherborne, Dorset, DT9 3QN, United Kingdom
Head’s name
Ruth Sullivan
Shiplake College
Age range
11 - 18
Location
Shiplake, Henley-on-Thames, Oxon, RG9 4BW, United Kingdom
Head’s name
Tyrone Howe
Shrewsbury International School Bangkok
Age range
2 - 18
Location
1922 Charoenkrung Road, Wat Phraya Krai, Bang Kho Laem, Bangkok 10120, Thailand
Head’s name
Robert Millar
Shrewsbury School
Age range
11 - 18
Location
The Schools, Shrewsbury, Shropshire, SY3 7BA, United Kingdom
Head’s name
Leo Winkley
Sidcot School
Age range
3 - 18
Location
Oakridge Lane, Winscombe, North Somerset, BS25 1PD, United Kingdom
Head’s name
James Jones
Sir William Perkins’s School
Age range
11 - 18
Location
Guildford Road, Chertsey, Surrey, KT16 9BN, United Kingdom
Head’s name
Debbie Picton
Solihull School
Age range
3 - 18
Location
793 Warwick Road, Solihull, West Midlands, B91 3DJ, United Kingdom
Head’s name
Charles Fillingham
South Hampstead High School
Age range
4 - 18
Location
3 Maresfield Gardens, Hampstead, London, NW3 5SS, United Kingdom
Head’s name
Anna Paul
St Albans High School for Girls
Age range
4 - 18
Location
Townsend Avenue, St Albans, Hertfordshire, AL1 3SJ, United Kingdom
Head’s name
Amber Waite
St Albans School
Age range
11 - 18
Location
Abbey Gateway, St Albans, Herts, AL3 4HB, United Kingdom
Head’s name
Joe Silvester
St Aloysius’ College
Age range
3 - 18
Location
45 Hill Street, Glasgow, Scotland, G3 6RJ, United Kingdom
Head’s name
To be confirmed
St Andrew’s Cathedral School
Age range
3 - 18
Location
Gadigal Country, Sydney Square, Sydney NSW2000, Australia
Head’s name
Dr Julie McGonigle
St Andrews Turi
Age range
3 - 18
Location
Molo, Nakuru County, Kenya
Head’s name
Geert Simons
St Bede’s College
Age range
3 - 18
Location
Alexandra Park, Manchester, M16 8HX, United Kingdom
Head’s name
Maria Kemp
St Benedict’s School
Age range
3 - 18
Location
54 Eaton Rise, London, W5 2ES, United Kingdom
Head’s name
Joseph Smith
St Catherine’s British School
Age range
3 - 18
Location
Leoforos Venizelou 77, Lycovrissi, Athens, 141 23, Greece
Head’s name
Jon Perriss
St Christopher’s School
Age range
3 - 18
Location
PO Box 32052, Isa Town, Kingdom of Bahrain
Head’s name
Simon Watson
St Columba’s College, Dublin
Age range
12 - 18
Location
Whitechurch, Dublin 16, D16 CH92, Republic of Ireland
Head’s name
Mark Boobbyer
St Columba’s College, St Albans
Age range
4 - 18
Location
King Harry Lane, St Albans, Hertfordshire, AL3 4AW, United Kingdom
Head’s name
Karl Guest
St Columba’s School, Kilmacolm
Age range
3 - 18
Location
Duchal Road, Kilmacolm, Scotland, PA13 4AU, United Kingdom
Head’s name
Victoria Reilly
St Dunstan’s College
Age range
3 - 18
Location
Stanstead Road, Catford, London, SE6 4TY, United Kingdom
Head’s name
Nicholas Hewlett
St Edmund’s College
Age range
3 - 18
Location
Old Hall Green, Ware, Hertfordshire, SG11 1DS, United Kingdom
Head’s name
Matthew Mostyn
St Edmund’s School, Canterbury
Age range
3 - 18
Location
St Thomas Hill, Canterbury, Kent, CT2 8HU, United Kingdom
Head’s name
Edward O'Connor
St Edward’s School
Age range
13 - 18
Location
Woodstock Road, Oxford, OX2 7NN, United Kingdom
Head’s name
Alastair Chirnside
St George’s College
Age range
3 - 18
Location
Guido, Quilmes, Buenos Aires Province, Argentina
Head’s name
James Diver
St George’s College North
Age range
3 - 18
Location
General Mosconi, Los Polvorines, Buenos Aires Province, Argentina
Head’s name
Oliver Proctor
St George’s College Weybridge
Age range
11 - 18
Location
Weybridge Road, Addlestone, Surrey, KT15 2QS, United Kingdom
Head’s name
Rachel Owens
St George’s College, Zimbabwe
Age range
13 - 18
Location
Borrowdale Road, Harare, Zimbabwe
Head’s name
John Farrelly
St George’s British International School, Rome
Age range
3 - 18
Location
Via Cassia km16, La Storta, 00123 Roma RM, Italy
Head’s name
Dr John Knight
St Helen and St Katharine
Age range
9 - 18
Location
Faringdon Road, Abingdon, Oxfordshire, OX14 1BE, United Kingdom
Head’s name
Rebecca Dougall
St Helens’s School
Age range
3 - 18
Location
Eastbury Road, Northwood HA6 3AN, UK
Head’s name
Bridget Ward
St John’s School
Age range
11 - 18
Location
Epsom Road, Leatherhead, Surrey, KT22 8SP, United Kingdom
Head’s name
Alex Tate
St Julian’s School
Age range
3 - 18
Location
Quinta Nova, Avenida Jorge V, 2775-588 Carcavelos, Portugal
Head’s name
Paul Morgan