The origin of the Old Boys’ Association in the early years is obscure and its records scanty. Documentary evidence found in the school magazine the “School Review” of 1936 states that Rev. Abel Eklund, the second Principal of ACS Klang, helped to organize the OBA in 1925. Consequently the earliest record pertaining to the OBA was a letter written by an old boy, the late ASP Leong Boon Swee who was stationed in Ipoh, to the school regarding the Old Boys’ meeting and reunion dinner held on 15th November 1957 in which he stated “I am most interested in the Klang ACS OBA as I was the first President when it was formed in 1926. I still have a photograph taken on the occasion but I am unable to locate it at the moment.

The members of the OBA were scattered and it was not possible for them to meet very often and function effectively. It existed as an organization of Old Boys and came to life as and when an occasion arose. Various attempts had been made to revive the OBA over the years.

In 1936, Rev. Abel Eklund and his wife returned to Klang after an absence of ten years. Old Boys responded to the call of their Alma Mater again and on the morning of 7th November 1936 nearly 100 of them gathered at the old MGS Hall (Methodist High School now) in Jalan Bukit Jawa, Klang. On that occasion Old Boys from all walks of life – magistrates, doctors, leading businessmen, etc – mingled freely. They were welcomed by Rev. Abel Eklund who urged them to revive the OBA. The meeting resuscitated the OBA, and Che Ahmad bin Haji Mahmood was elected the President with Mr. G.S. Arumugam as the Hon. Secretary.

According to the “School Revive” of 1938, another Reunion Day of ACS Old Boys was held on 22nd October 1938. An elaborate sports programme had to be abandoned due to rain. However, football enthusiasts among the Old Boys played and defeated the schoolboys. At 6.00 pm the Old Boys attended the Annual Concert by the boys of the school to which they were specially invited. The Reunion Dinner which was the most important event of the day attended by more than 250 Old Boys was held at the new hall of the MGS in Bukit Jawa Road. Speeches were made by Mr. J. R. Neave, Dr. M. Gabriel, Messrs  Edward I. Ponniah, Chan Ho Keng, G.S. Arumugam and Rev. Abel Eklund.

The grand gathering of Old Boys and friends and the festive appearance of the new hall was indeed an occasion which could not be easily forgotten by those who were present. Before the dinner a Committee was elected with Mr. Goh Tiang Chin as President and Mr. G. S. Arumugam as Secretary, Representatives (three to seven) for Klang, Port Swettenham (as it was known then), Kuala Selangor and Kapar, Kuala Lumpur, Negeri Sembilan, Perak, Pahang and Singapore were also elected. The most serious attempt to revive the OBA was made when Mr. D. R. Daniel, the Principal, organized a meeting of Old Boys in the school hall on Friday, 15th November 1957 with the help of Mr. Goh Tiang Chin, a leading Old Boy at that time, and Mr. Koh Liang Sih, a senior teacher of the school. The meeting was presided by Mr. Goh Tiang Chin. The District Officer of Klang, Tuan Syed Hashim bin Abdullah and the Principal, Mr. D. R. Daniel, addressed the Old Boys. A protem committee was elected with Encik Mohd. Noor bin Abu Nawas as President and Mr. C. E. Benjamin as Secretary. One of the first tasks of the Committee was to draft the Rules and register the Association. Before the meeting, badminton and volleyball matches were played between the Old Boys and the students for which trophies were donated by the District Officer. A Reunion Dinner was held on the same evening at the Evergreen Restaurant, Klang. The OBA was finally registered on the 11th February 1961.

The Inaugural General Meeting was held on Saturday 21st October 1961 in the School Hall and was attended by 52 Old Boys. The first properly constituted Committee was elected comprising 11 members with Mr. Koh Liang Sih as President and Mr. A. Ramanathan as Hon. Secretary.

Annual General Meeting and Reunion Dinners have since been held without a break since the meeting and reunion dinner mentioned above with dinner attendance around 600 – 700 participants in recent years.

The OBA participated actively in the ACS Centenary celebration in 1993, with our President, Mr. Jimmy Yeoh Joo Chuan as chairman of the Centenary Celebration Committee and with Mr. Ng Seng Gong, a Committee Member cum Social Chairman, as chairman of the Centenary Dinner Committee. Several Old Boys also served in both the committees.

In consonance with the OBA’s motto “Fellowship and Progress” the OBA strives to promote the esprit de corps amongst its members by organizing various activities which are highlighted in the Sub-Committee Reports.

Over the years the OBA has increased its membership and extended its activities and even more progress and expansion can be accomplished with members’ support and encouragement so that the OBA can develop into an organization Old Boys will truly proud of.

The OBA celebrated its Silver Jubilee (25 years) in 1986, culminating in a grand Dinner at the Neptune Restaurant, Kuala Lumpur on Saturday, 12th April 1986.

The OBA celebrated its Golden Jubilee (50 years) in 2011 culminating likewise in an even GRANDER dinner at the Premiere Grand Ballroom, Klang on 27th August 2011. Over 750 Old Boys, their family members, friends, supporters and guests participated in the auspicious function.