High School Gerrit Maritz commenced on 16 January 1956 on the premises of Pretoria-Noord High School, with 182 students and 9 teachers, led by Mr. J P Malan as the Acting Principal, under the name 'Pretoria-Noord Second High School'. With the start of the second quarter of that year, Pretoria-Noord Second High School moved to a site on the opposite side of the current Rosslyn Road. A new and permanent building on the southern side of Rosslyn Road was occupied in October 1960, gaining the name High School Gerrit Maritz.

It was in the year (1960) that the High School had its first Grade 12 class. The school grew and developed its own unique character. In all areas of school life—academics, culture, and sports—the school flourished and established its esteemed position among Pretoria's schools. Over the next twenty-five years, student numbers grew to the point where High School Gerrit Maritz was recognized as one of the largest Afrikaans schools in the world in the early 1980s. With a student count of 1534 in 1987, a portion of the Grade 8 students transitioned to the new Hoërskool Akasia.

The identity of High School Gerrit Maritz is not solely shaped by its students, but also by a multitude of teachers who have taught or are still teaching here at some point. Six principals have, during the school's existence, rallied the intellectual and physical potential of its students and teachers, establishing a unique school north of the Magaliesberg mountain range.