Officer Candidate School or OCS is the term given for the training given to enlisted men or new recruits who are slated to become commissioned officers. All branches of the Federation military have one, although Earth Fleet prefers to have officers who have attended the Fleet Academy on Avalon. Light Infantry also provide direct commissions for several of their divisions.
Because not all awakened humans actually awaken before their 16th birthday and they become elligible for the draft, some of them make it into college or even graduate before gaining their magical abilities, and these lucky few can either enter the Tech Infantry directly as an officer (if they already graduated) or obtain a draft deferrment to finish college and then enter as an officer upon graduation. For everyone else, OCS remains the only route for enlisted Tech Infantry officers to become commissioned officers. Their belief is that experienced troopers are the most ikely to become good officers, and "college boys" generally actually are slower to be promoted and obtain combat commands.
OTCOM (Tech Infantry Officer Training Command) was located on Avalon and involved nine weeks of intensive physical and mental instruction. A small facility has been set up on New Madrid since the Holy Terran Empire took over on Avalon, but in the present emergency, limited resources mean only a few slots are available for the best candidates. In cases where commission is necessary but transport is unavailable, training can be provided through a viral-injected training module, which simulates the training time in the candidate's head. However, most TI leadership still prefers to have their candidates to go through the physical experience, rather than deal with the potential mental side effects.
Behind the Scenes
Although we assume all our officer characters have gone through this, it rarely gets played out. The one example was Alistar Dimiye's promotion from Sergeant to Captain among the Tech Infantry Rebels where he gets the viral education.