John Gray High School had its earliest beginnings in 1946 during the centenary celebration of the Presbyterian Church of Jamaica and Grand Cayman, when the idea of starting secondary education run on British lines in Grand Cayman was discussed.
The Cayman High School didn't begin, however, until January 1949 when it was opened by Rev. George Hicks, a Church of Scotland missionary in Grand Cayman since 1936, who was also an Inspector of Schools for the Cayman Government.
Rev. Hicks asked Rev. John Gray, a Scottish missionary associate of his during his time in Jamaica, to take over the running of it and to assist with the ministry work. Rev. Gray became headmaster in April 1949.
At that time, the school had only three teachers plus the headmaster and a handful of students, but was successful in the Senior Cambridge Examinations, with thirty three students gaining passes between 1952 and 1962.
Funding was always difficult for the church and government began financial assistance in 1961 and took over complete control in 1964. Government ran two high schools, the Cayman High School, which was a grammar school and the Secondary Modern, which was a technical/vocational school.
These two schools were amalgamated into a senior comprehensive in September 1970, which grew steadily in enrollment until it topped one thousand students and became increasingly difficult to manage.
The Cayman Islands Middle School was hence begun in September 1979 as a junior high feeding the Cayman Islands High School which became a senior school. These two schools grew to be equal in size and were renamed George Hicks High School and John Gray High School, respectively, in September 1992.