ISKL began with a modest start in 1965 in Istana Tetamu, on Jalan Maxwell, following several months of planning by the first head of school, Robert Fendley, Dr. Luebke of the Office of Overseas Schools and school board members. With nine teachers and 48 students in the sixth, seventh, eighth and ninth grades, the academic courses were based on an American curriculum.

When Al Chudler arrived in 1968, he inherited a school where enrollment was rapidly increasing due to the influx of oil companies investing in Malaysia. The fine arts and athletics programs were thriving and the first inter-school debates and sports activities were organized with Singapore American School. This marked the beginning of a friendly rivalry that continues to this day. By the end of this decade there were nearly 400 students from 24 countries.