Hoerskool Gerrit Maritz started on 16 January 1956 on the grounds of Pretoria North High School, with 182 pupils and 9 teachers under the guidance of Mr. JP Malan as acting Principal and with the name Pretoria North Second High School.

With the start of the second term of that year, Pretoria North Secondary High School moved to a site on the other side of the current Rosslyn Road. A new and permanent building, on the south side of Rosslyn Road, was occupied in October 1960 and acquired the name of Gerrit Maritz High School.

It is therefore in the year (1960) in which the High School has its first grade 12 class. The school grows and develops its own and unique character. In all areas of school life, academia, culture and sport, the school grows and takes its appreciated and recognized place between the schools of Pretoria. During the next two and a half decades, the learner numbers increase to the extent that Gerrit Maritz High School was referred to as the largest Afrikaans school in the world in the early 1980s. With a pupil number of 1534 in 1987, a part of the Grade 8 pupils goes to the new Hoërskool Akasia.

The character of Gerrit Maritz High School is not only shaped by its learners, but also by a large number of teachers who at one stage or another have taught here and still do. During the period of the school's existence, six principals also mobilized the mental and physical strength of its learners and teachers to establish a unique school north of the Magaliesberg.