- Philatelic & Numismatic Society
- Robotics Club
- Yoga Club
- Library Club
- Environmental Club
- College Magazine
- Chamber Orchestra
- Cinema Society
- Astronomy Club
- Aquarium Club
- Scuba Diving Unit
- Culinary Arts Society
- Aeronautical Societya
- Junior Science & Technology
- Histoarcheo Club
- Geography Society
- Gavel Club
- Student Christian Movement
- English Lit & Debating Society
- Radio Club
- Junior Maths Society
- Road Safety Patrol
- Sinhala Literary & Debating Society
- Seylan Bank Students’ Savings Unit
- HNB Students’ Savings Unit
- Kennel Club
- Buddhist Students’ Association
- Junior English Lit & Debating Society
- Art Club
- Spelling Union
- Carnatic Orchestra
- Canto Perpetua Choir
- Western Band
- Tamil Drama Society
- Hewisi Band
- English Drama Society
- Photographic Club
- Society for Social Work & Welfare
- ICT Society
- Senior Environmental Club
- Hindu Students’ Union
- Political Science Society
- Red Cross Society
- Association of Innovation and Design
- Islamic Society
- Association of Science and Technology
- Quiz Club
- Automobile Club
- Cubing Society
- Health Club
- Tamil Literary and Debating Society
- Wildlife Society
- Thomian Union
- Commerce Society
- Interact Club
- The Ternion
- Classical Music Association
- Media Unit
- Productive Citizenship Society
- United Nations Club
Scuba Diving Unit
The S. Thomas’ College Sub-Aqua Club (STCSAC) was the brainchild of two old boy diving enthusiasts of the school. We are now the old boy support group to the S. Thomas' College Scuba Diving Unit (STCSDU), an extra curricular activity classified as a sport since February 2015. Our training programme introduced at inception has evolved over the years and is best judged by the quality of divers we continue to produce to date. We look forward to seeing you and hope you’ll join the club! https://www.stcsac.lk/the-club/join-usLatest Project
Jan to Apr - AGM (Jan) - Exhibition Dive at the OBA lunch (Feb) - Participation at Rendezvous (Feb) - Reef/wreck Clean-up (Feb/Mar) - Low visibility dive expedition (Feb/Mar) - Dive trip Hikkaduwa/Kalpitiya (Mar/Apr) - First Aid Programme (Mar) May to Sep - Monsoon Fin - STCSAC vs STCSDU Underwater Hockey Tournament - STCSAC vs SLSAC Underwater Hockey Tournament - Dive trip East coast - Record breaking challenge Oct to Dec - Beach Clean-up (Oct) - Exhibition Dive at the Lower School Swimming Gala (Oct) - Dive trip down south (Dec) - Christmas party