Sometime early in 1991, Venerable V.S Adenugba met with Dr. Adetomiwa George, Overseer A. Badejo and Mrs. Gbemisola Awoyungbo (NEE Oresusi). This meeting led to the formation of The Apostolic Church Grammar School Old Students' Association (TACGSOSA). Prelude to the eventual formation of TACGSOSA with a constitution, eleven monthly meetings were held at the Festac home of Dr. Olanrewaju Adetomiwa George.

The Aims and Objectives of the Association which are set out in article III of its constitution include: Provision of a link between the School and its old students, to assist the school, help members etc. On 15th January, 1992, the inaugural Annual General Meeting (A.G.M) took place and the following pioneer Executive committee members emerged:- President (Otunba Adewole Odumbo), Vice President (Dr. Adetomiwa George), General Secretary (Mr I. O. A. Babalola), Assistant General Secretary (Mrs. Taiwo Fajingbesi), Treasurer (Dr. Olorunfunmi Johnson), Financial Secretary (Mr. J.O. Emiola), Venerable V.S. Adenugba was the Chairman of the inaugural AGM which was well attended by members including Otunba Alex Onabanjo, Mrs Bimbo Jeboda, Mrs Olubunmi Oyelele, Mr Dapo-Atoloye etc. The then School Principal Mrs M.V Farinu attended the AGM with other members of Staff.

Elections are held every 2 years and the current Executive members are listed under a separated heading. As part of its activities, Annual Dinners/Luncheon are held. Records of such since inception are: 1992 (hosted by members at the School Hall), 1993 (Hosted by Mrs. Fajigbesi at Akiode Village), 1994 and 1995 (Hosted by Mr & Mrs. Dipo Daramola at gbagada),1996 (Hosted by Mr and Mrs I.O.A. Babalola). 1997 - 2001 held at Sheraton Hotel and Towers, Ikeja. The twelfth and the thirteen held at CHEVRON CLUB Soluyi Estate, Gbagada. The fourteenth & fifteenth held at the Lagos Airport Hotel, Ikeja. The sixteenth held in the School Compound. The seventeenth was held on the 24th January 2009 within the school compound.

Members participate actively in the activities of the School especially in areas of Career Guidance and Counselling, Annual Prize and Speech Day, School Anniversary and other areas.

TACGSOSA embarked on the construction of an Introductory Technology Laboratory Building for the school as part of efforts by members to raise the standard of education.