St. Thomas Aquinas Senior High School was established on 15th January, 1952 at Osu Anahor, a suburb of Accra at a time when the then Catholic Diocese of Accra felt the need for a Catholic Boy's Secondary School in Accra. The then Bishop of the Diocese, Rt. Rev. A.A. No_ser S.V.R gave the task to the late Rev. Fr. Alphonse Elsbemd, who opened the School with an enrolment of fifty (50) students in Forms One and Two.. The initial staff of five consisted of Fr. Alphonse Elsbernd, Fr. George Wilson, Fr. Fisher, Mr. Augustine Adu and Mr. Paul Baddoo.
In November 1955, the first candidate (one person) was presented for the General School Certificate Examination and had a 100% pass. 
In September 1963, Aquinas moved to its present location in Cantonments and in 1973, a Sixth Form education was introduced in the school. Presently, the school runs nine (9) streams and five Academic Programmes. Enrolment level now stands at 1,200 with a Teaching staff strength of sixty five (65) and a non-teaching staff of thirty five (35). Mr. Francis Ahiafor is the current Headmaster as well as the eleventh (11TH) Headmaster of the school.