Old Bo Boys Association (OBBA) is an organisation of ex-pupils of Bo School and it came into existence during the principalship of Mr Vincent F. De Lisle. The notion of forming OBBA was initially pioneered by an ex-pupil, Mr Amadu Wurie (Admission Number: 55) in 1927, when he sent a circular letter to all ex-pupils of Bo School requesting additional funds for the development of the school. The letter sent by Mr. Amadu Wurie was supported by the then principal of the school, Mr. Vincent F. De Leslie. However, it was not until 1928 that the then principal, Mr Vincent De Lisle, got an approval from the Sierra Leone Government to start OBBA. In March 1929, an inaugural OBBA meeting was held in Bo that led to the establishment of a number of chapters of OBBA with. Mr. Vincent F. De Leslie becoming OBBA’s first president with Mr. Amadu Wurie, its first secretary.

The inception of OBBA was embraced by ex-pupils of the Bo School both nationally and internationally, especially in the United Kingdom, where in 1953, ex-pupils of the Bo School studying in Britain started a branch of the Association in London –OBBA (UK). Other branches of OBBA have since been developed all over the world, for example, in most states of the USA and Canada.

The principal aim of OBBA then and now is to reaffirm ex-pupils’ devotion to their alma mater, develop and strengthen relationships between ex-pupils (in Sierra Leone and abroad) and the Bo School and to help bring further improvement in the school. OBBA's main source of funding is from its membership through subscription and charitable donations from individual Branches, individual ex-pupils and well-wishers.

OBBA and the Bo School have made several contributions to the educational, economic, social and cultural development of Sierra Leone in many ways. In his speech to members of OBBA on the occasion of the Jubilee celebration in March 1979, His Excellency Dr. Siaka P. Stevens, first President of the Republic of Sierra Leone, stated: “Bo school has been a trail blazer in the annals of Sierra Leone's education progress in more ways than one. While serving as a centripetal force for various ethnic groups at a formative level, the school at the same time provided a halo from which surrounding peoples benefited immensely. In the new national system, your role should be even easier. I congratulate members of OBBA on the occasion of the Golden Jubilee Celebration. Much to the pleasure of succeeding generations of administrators, the school has been exerting a wholesome influence disproportionate to its foundation. Indeed the history of Provinces might have been different without the leadership products of the school in chieftaincy and other fields of endeavor. The enviable reputation and distinguished role of your products in nation building should be maintained if the school is to count in the nation's esteem.”

Since the inception of OBBA, Presidents, Vice Presidents, Ministers and senior Civil servants have all been associated with OBBA and have enthusiastically participated in OBBA celebrations. Recently, President Ahmed Tejan Kabbah became a honorary pupil of the Bo School.

On 13 April 1974, OBBA presented a new library building to the school, the Dr. Drissa Yilla Memorial Library. The Golden Jubilee was celebrated in 1981. The Bo school endowment fund was formally established on 20 April 1984 with a target amount of Le1, 000,000 which was to be subscribed over a period of ten years,1984-1994.

In 1979, Abu A Koroma was popularly elected National President of OBBA to succeed Paramount Chief R .B. S. Koker. President Abu A. Koroma revived OBBA and extended its activities to regions throughout the country. When Dr. Sama S. Banya became OBBA National President afterwards, he was able to secure the present marching band for the school in 1997 which is now the pride of the school.

At the 61st annual meeting of OBBA in April 1990, Alie Dausy Wurie, (Admission Number: 307), initiated the two classroom-building project to be undertaken by OBBA. The buildings were later completed and furnished by the Wurie family. With input from the Ministry of Education, the buildings were dedicated to the memory of Korthor A. D. Wurie at OBBA 2000.

In March 2000, a new national executive was elected with Late Hon. A. O. Bangura as President, succeeding Dr. S. S. Banya. A new Board of Governors was constituted with Dr. T. O. Matturi as Chairman, succeeding Dr Momodu Yilla in January 2001, Mr. Raymond Bob Katta was appointed Principal of the Bo School to succeed the longest serving Principal in the history of the School, Mr Festus M.Seiwoh, 1978-2000.

Bo School will be 100 years in 2006. It is the wish of OBBA to present a new dormitory to the school as a special gift on the occasion.