Assumption College traces its history to 1885, when Reverend Father Emile-August Colombet, a
Roman Catholic French missionary priest, opened a school in Bangkok. In those days before free public schools, Colombet realised many Thai children went without an education. Buddhist monks taught reading and writing in their temples, but attendance was not compulsory. Father Colombet opened his own primary school to help fill the need. The church school, named the Thai-French School, which used French and Thai as the medium of instruction. Father Colombet's school was in an ordinary wooden house. Classes at the beginning were small; his first student was a Chinese-Thai, Siew Meng Tek. The number of students steadily increased; today more than 57,000 boys have been educated at Assumption College. On 16 February 1885, the school was formally established under the name of Collège de l'Assomption. On the first day of school, there were 33 students. After that the school gradually became known and the demand for a new study hall was needed. Colombet sent a letter to King Chulalongkorn and the queen and solicited contributions and donations from noblemen and Thai and foreign merchants in Bangkok. The school became well-endowed. On 15 August 1887,
Crown Prince Maha Vajirunhis represented King Chulalongkorn in laying the cornerstone for the construction of the first study hall, later named the "old building" (Thai, "tuek gao"). In 1900, Father Colombet returned to France. He asked the
Montfort Brothers of St. Gabriel to assume management of Assumption College. On 20 October 1901, the Superior General of the Brothers of St. Gabriel sent five reverend brothers to Thailand in order to continue the initiative of Father Colombet. They were Rev. Bro. Martin de Tours (the second director), Rev. Bro. Arbaire, Rev. Bro. Augustine, Bro. Gabriel Ferreti, and Rev. Bro. Hilaire, who pursued the objectives of Father Colombet. Assumption College was the first boys' school of the St. Gabriel Foundation in Thailand. In 1910, the school changed its name from Collège de l'Assomption to Assumption College or AC. When the number of students sharply increased, the existing study hall could not cater to the increasing numbers. At that time, the
Brothers of Saint Gabriel established Assumption College Primary Section in 1965 in Sathon, Bangkok, on an area of six
rai. The primary section was approved and opened on 22 May 1966. The school was officially opened and blessed on 6 May 1967 by Archbishop Joseph Khiamsun Nittayo and Mom Luang
Pin Malakul. The minister of education presided at the ceremony. In 2002, during Brother Surasit Sukchai's term of governance, the English programme (EP) was introduced to serve students who wanted to prepare themselves for international study. The program started in Prathom Suksa 1 and in Mathayom Suksa 1 in the first year. Now the program offers complete primary and secondary levels or from Prathom Suksa 1 to Mathayom Suksa 6. == School symbol==