The "Inst" community does not just comprise the boys currently at the school, their parents, and the staff. A very important part of that community is the body of the old boys of the School known as Belfast Old Instonians Association. The Association was formed in 1911, one year after the School celebrated its centenary. Those who promoted its formation had a vision of

"an organisation which may draw together those who have had common school experiences and common memories of youth, and who, as they are united in loyalty to the School, and in desire for its welfare, may remain likewise united and bound to one another in whatever part of the world they may find themselves".

And these sentiments still find expression in the constitution of the Association, setting out its objects as sustaining and deepening interest of former pupils in the School, furthering the welfare of pupils and former pupils of the School, and strengthening the feeling of kinship among Old Instonians.

Links between the old boys and current pupils are manifold. Members of the rugby, hockey, cricket, and golf sections of the Instonians sports club coach and play matches against their counterparts in the School. Old boys offer careers advice, and provide work experience for boys at the School. The Council of the Association will consider suitable requests for financial assistance from sports clubs engaging in foreign tours and from individual boys seeking to further their personal development in special expeditions.

Opportunities for social intercourse among the old boys themselves are not forgotten. The annual dinner, held at the end of each October, with reunion tables for 20, 30, 40 and 50 year school leavers, is the best attended event of its kind in Northern Ireland. A popular dinner is held in London each Spring; in early summer there is an informal buffet evening at the Shaws Bridge pavilion; and, very importantly, around Christmas the Association is delighted to entertain the boys who left the School the previous June at a "curry evening".

Membership of the Association is open to all who have attended Inchmarlo or Inst, and to all members of the staff at either school, and is a prerequisite for membership of the Instonians sports club by those who are eligible to join the Association. It is the earnest wish of the Association that all former pupils of the School join the Association to carry on a great tradition which started in 1911.