The House system is an integral and vibrant part of the ST. THOMAS SCHOOL culture. The House system is designed to reflect and enhance the spirit of competition and sportsmanship. The House system aims to give students an identity and sense of pride in a supportive, secure environment. At the same time this system provides an ambience for positive competition and a closer rapport between students and teachers. All the students from class I upwards are divided into 4 houses which form the 4 cornerstones of the school. The houses are named : COURAGE (Blue), HONOUR (Red),  ENDURANACE (Green) and VALOUR  (Yellow).

Each house is led by a girl house captain and a boy house captain. Every house is also allocated a teacher designated as the house warden. Marks are awarded to the houses throughout the year for extracurricular activities through Inter-House competitions in sports, dramatics, debates, quiz, art and music. At the end of the year, the house bagging the highest score is awarded the championship trophy. the special events are: