Although some interschool competition did exist prior to 1968, the first real championship was held in Zurich in 1968 in soccer for boys and volleyball for girls. The organization in the 2012-2013 now boasts a membership of twenty three (23) international schools consisting of both full member and sport member schools.

The ISST is fundamentally a Varsity athletic organization which governs competitive athletic championships for its 23 member schools. The ISST currently sanctions 12 sports annually across two divisions for 22 Varsity championships in soccer, volleyball, field hockey, cross country, rugby, swimming, basketball, softball, baseball, tennis, golf and track and field plus three (3) Junior championships in the sports of cross country, swimming and track and field.

The organization is controlled by the Athletic Directors of the Full Member schools. The ISST is managed by an Executive Committee (EC) consisting of a Chairperson, a Secretary, a Treasurer and three (3) ISST Athletic Directors (one of whom must be from a Sport Member school).

Following the first championship, a meeting chaired by John Griffin, Superintendent of the American School of the International Schools of The Hague, was held to explore interschool links in sports, drama, art and music. This meeting formed the basis of the International Sports League (I.S.L.) which had four regular members – the American School of The Hague, Frankfurt International School, the International School of Brussels and the American School of Paris and three guest members – the American School in London, Zurich International School and the American International School - Vienna. This league never really functioned as a league due to excessive costs in time and money. The result of this non-function was the establishment of end-of-season championship events. In 1970-71 it was decided to reform the league as simply a championship organization, thus founding the ISST.

Burton Maclean of ASP became the chairman of the organization and gave several ADs the mandate to establish rules and regulations and to formalize the championship structure. For the majority of the seventies, Dr. Lewis Grell of ASH strengthened the ISST and supervised the increase in sporting opportunities for both boys and girls.

Miles Lovelace of the Stavanger American School in Norway steered the organization through the early eighties before handing the task to Bob Ater of ISB, who was responsible for establishing a more democratic and enlarged membership. In the late 80’s Brian Duncan of ACS Hillingdon accepted the chair and remained in that position until the mid 90’s when Ray Taylor of the Munich International School assumed the role.

From 2002 until his untimely death in 2005, Executive Secretary Eddie Hufford of ASL chaired the organization. The original Secretary, Karl Hainaut from ISB, remained in the office for one year, and Eddie Hufford continued in that role until 2005. The ISST is presently managed by an Executive Committee, with the chair of that committee presiding over the three annual Athletic Directors’ meetings.

The establishment of dual championships (Alpha and Omega) occurred to meet the desire of all members to participate in interscholastic sports. This subsequently trans-morphed into Divisions 1, 2 and 3 in selected sports.

The original design of the ISST logo was made by Dave Schaefer, AD at St John’s. Originally, it was more in the shape of a basketball with the initials ISST making up the panels of the ball. Although the design has changed, the original colors (green and white from St. John’s) are still used for the All-Tournament patches awarded in most of the championships.