Early alumni of KIS include US Ambassador to India Robert F. Goheen (1936) and US Senator Chris Van Hollen (1977).

[10] In the early 1880s, there was a great need for an English-medium school in South India, due to an ever-increasing Christian mission community in the area.

Having a school at a hill-station would allow the children of missionaries to escape the tropical diseases that were claiming the lives of so many, and provide a cool and open atmosphere that stimulated learning.

Seeing the need for a school, and also realising that the missionaries could not find the means to establish one, she decided to begin the process herself.

After commissioning The Highclerc Hotel as a building more than a year later, under the leadership of Mrs. Margaret Eddy, "Highclerck School" was opened to students on 1 July 1901.

By 1902 the owners of the building had drastically increased the rent, so the school was moved to Rock Cottage and Central House.

In 1905, Mrs. Eddy returned to Kodaikanal, and was able to buy The Highclerc Hotel from its new owner for INR 29,000 along with 3.5 acres (14,000 m2) of land.

Mrs. Eddy served as principal of Kodai School, without salary, from 1901 to 1905, when she was forced to return to the America due to a sickness.

Another major change in the school occurred during this time – nationalism was becoming more and more visible in the world, and the American missionary exodus from India began.

Several international companies endowed grants upon the school in return for guaranteed places for students.

Robert Carman ('48) worked with Frank Jayasinghe, the new Director of Development, to produce Project Design, a document which outlined the mission, philosophy, and expectations of students within the school.

[10] In 2006, KIS officially was granted its request to follow the IB Middle Years Program curriculum for grades 6–10, and it began issuing MYP Diplomas.

SoEx groups have worked in orphanages, taught and assisted in local school support programs and been involved in village planning and tribal community development projects.

Every Saturday, there is a SoEx activity in which all students can voluntarily participate; such as a visit to the Shenbaganur Orphanage, the Mercy Home, or the village school.

Many NGO's are based within Kodiakanal and the school often has programs in which students will help these charities through documentation and the raising of funds.