Cathcart High School began when the doors for a non-denominational school opened in March 1879 in a wood and iron building opposite the present Dutch Reformed Church in Hemming Street. The school’s enrollment was 26 pupils—13 boys and 13 girls.
Enrollments grew to 55 pupils in 1881. The new school buildings were erected and opened on 1 September 1900 in Barrack Street, the present school premises.
By 1949, the school enrollment had increased to 240 pupils and a new wing was added to the school.
In 1952, the foundation stone for the Memorial hostel , honouring the fallen during World war II, was laid by the headmaster from 1939 to 1951, Mr W.A.Clarke . This hostel is now a junior hostel called the Annexe, housing 100 boarders.
The present Memorial hostel for senior boarders was opened on 14 April 1984 and now houses 130 boarders.