Due to the outstanding success of the Boys Company, the Queen's Regimental Army decided to expand the school's size. The school was upgraded with the addition of 3 more companies. The school was re-christened Nigeria Military School. The 4 companies were named Enugu, Lagos, Ibadan, & Kaduna Houses. The focus of the training at the Nigeria Military School began to change with more attention given to academics than was previously done. This led to the schools' certification by the West African Examination Council (WAEC).

In 1974, the names of the companies were changed to Alpha, Bravo, Charlie & Delta companies. Each company was assigned a color. Blue, Yellow, Red, Green, Purple & Maroon respectively. The school continued to grow, and to accomodate this growth two more companies were created. These were called Echo & Foxtrot Companies, with company colors of purple & maroon respectively.

Discipline in the Nigeria Military School (NMS) has always been of paramount importance. There is a well-established chain of command which starts from the junior boy up to the schools' Boy Regimental Sergeant-Major (B/RSM).

Unlike other secondary schools in Nigeria, NMS provides military training to its students comparable to that found in any military formation. The only other school with a tradition similar to that of NMS is the Airforce Military School, Jos. But they don't come close to NMS in any way.

Having passed through the rigors of NMS a boy comes out toughned and ready to take on the challenges of being a professional soldier. Consequently, a large percentage of graduands are posted to military units around Nigeria to serve as soldiers. Some of these students go on to the Nigeria Defence Academy where they become commisioned as officers in the Nigerian Armed Forces. Some other students opt out of military service after graduating, but as the saying goes "old soldier never dies".