MCJROTC stands for Marine Corps Junior Reserve Officer Training Corps. As opposed to the Reserve Officer Training Corps (ROTC), a JROTC program serves primarily as a "Leadership Education" course, teaching students about military structure, military history, ethics, etiquette, and helping to develop teens into functioning, positively influential members of society. There's no obligation to serve in the military, but military branches typically offer an immediate promotion after basic training to somebody who has completed a certain amount of time in JROTC (3 years if memory serves correctly).

A JROTC unit is organized similarly to a genuine military unit, depending upon the size of the unit itself. My unit only had about 100 people at any given time (which is rather small in all actuality), so we were a company. Other schools can have full battalions, which are comprised of multiple companies. Extracurricular activities that a JROTC unit would perform are pretty varied. My company visited Parris Island, Quantico, the Museum of Marine Corps History, and Splish Splash on trips (even marines gotta chillax.) Units often compete in drill competitions, practicing marching and the prompt and skillful execution of commands against other units, and participate in local events. I was the Marine Corps Flag Bearer for my unit's Color Guard for quite a while, and have done Honor Guards (Where you carry ceremonial sabres) twice. It's really quite fun if you invest time into it.