In the early 1920s, the KASS site was acquired from the Amakom chief by the English Church Mission (E.C.M.) with the intention of establishing an institution to train clergy, and facilitate the growth of the church in the Gold Coast.

Bishop M.S. O'Rocke (1913–23) secured the services of the monks of the Benedictine Order (O.S.B.) from Nashdom Abbey, England, to run the newly founded institution. In 1952, St. Augustine's Theological College was established.

In 1972 when the second Republic (under Prime Minister Dr. K. A. Busia) was overthrown by Colonel I. K. Acheampong, the new government decided that numerous training colleges would be converted into secondary schools or closed. Anglican Training College was listed as one of those to close. The staff, supported by their principal Fr Aggrey, signed a petition asking the government not to close the college, but to convert it into a secondary school to be called Anglican Secondary School, Kumasi.

The petition which was sent via the bishop, Rt. Rev. J. B. Arthur, who in turn wrote a covering letter approving of the petition. Both letters were forwarded to the then secretary of Education, Colonel Nkegbe in Accra. The petition was granted and in September 1973 Anglican Training College became Anglican Secondary School. It was a co-educational school but in 1987 stopped accepting girls as boarders. Fr P.D. Aggrey who was principal of the training college was retained as headmaster of the secondary school.He administered the school from 1973 to 1981 when he retired and was succeeded by Mr. John Poku between 1981 and 1986. In 1987. Mr. A. E. Kyere (a.k.a. Kontonkyi) assumed duty as the third headmaster of the school. It was under him that the school improved academically. In 1999, the school was for the first time, invited to take part in the National Science and Maths Quiz Competitions. Rev'd Canon E.Y. Brobe-Mensah, assumed headship of the school in November 2003, remaining in post until 2010