Following the public school tradition, S. Thomas' College is a partial boarding school, with some pupils living at the school seven days a week, and others residing in Day houses. Having been founded in 1851, it is among the oldest schools in Sri Lanka. With a student body of approximately 2800, S. Thomas' is considered as the most prestigious school in Sri Lanka. A factor leading to its competitive rivalry with Royal College, Colombo. This rivalry has led to a Royal–Thomian tradition with the annual Royal-Thomian Rugby Encounter and the Royal Thomian Regatta.