Had a discussion regarding this with a retired NCC
Officer.
My understanding is that teachers that are commissioned officers in
the SAF will hold a NCC rank equivalent to that rank. In other
words, if a LTA(NS) signs on with MOE and subsequently be in
charged of NCC in a school, upon completion of his NCC Officers'
Course ( Not too sure of the exact name of the course), he will be
commissioned as a LTA (NCC), while teachers that were non SAF
commissioned officers ( eg, WOSE, females teachers or teachers that
served NS in SPF/SCDF) will hold the rank of 2LT(NCC).
Likewise, if a NCC teacher who is holding LTA(NS) and LTA(NCC)
ranks gets promoted to Cpt(NS), his NCC rank will be emplaced to
that rank as well.
However, if one gets a NCC rank promotion, that will not affect the
NS rank, for obvious reasons. 
The few SAF Officers that were seconded to NCC, to the best of my
understanding are usually NSF 2LTs. The other comissioned SAF is
usually Commandant NCC. The other SAF personnels are non officers.
(Any NCC personnel can confirm this?)
