S. Thomas' Preparatory School (abbreviated as STPS) is a private, Anglican, multi-ethnic, primary and secondary day school for boys aged 5 to 16 years, located in Kollupitiya in the Colombo District of the Western Province of Sri Lanka.

He arrived in Ceylon in 1928 to join the staff of S. Thomas' College, Mount Lavinia, during the tenure of warden Kenneth McPherson.

Nevertheless, over the years the school began accepting older students, and currently has classes up to grade 11 in preparation for the GCE Ordinary Level examination.

7 of 1930) of which the chairman is the Anglican Bishop of Colombo, thereby retaining a connection between the church and the school.

Dushantha Lakshman Rodrigo assumed duties as headmaster on 1 January 2015[6] and continued to serve until 2021, when he was appointed the 16th Anglican Bishop of Colombo.

The four main faiths practiced by the students of the school, in descending order of frequency, are Christianity, Buddhism, Hinduism, and Islam.