It really depend on your unit.
Rumor claim that public schools like NUS sure get determent is a fake news. Public schools have common school holidays that allow uniform groups to have a better planning for call NSmen for ICTs during school holidays. Having lesson during ICT is never a value reason for deferment. The guidelines stated only for Exam!
However we know that there are NSmen who get rejected for deferment even the reason is Exam with supporting documents. As NSF/NSmen, we are dogs who has no right due to NS liabilities (and the only way is to study overseas in order not to be affected for your studies).
This applied to family commitment such as EDD for pregnant wife. Even Guidelines allow it, unit can disapproved your deferment. As NSF/NSmen, we are dogs who has no right due to NS liabilities (and the only way is to work overseas in order not to be affected for your family commitment). I almost kena before because NSSC recommend not to approved my deferment but my unit approved it.
The reason NSSC give is my unit's operating hours is office hours which is same like civilian job. However what NSSC do not know is once I report to my unit, I will report to my sub-unit (subordinate unit) and then attached to a unit not within my chain of command. The attached unit operated by shifts working hours. Some more for civilian job, I can take leave and if not approved, I can just AWOL and quit cause my family (pregnant wife and incoming new born baby) is more important then work. But for NS, we may not even get a Time Off or AWOL without MP to arrest me and put me in DB.
NSSC big mouth, don't know anything, don't anyhow recommend! I do not even know why stupid SAF want to get NSSC to be involved (unless it is for appeal for unsuccessful deferment application) since it is between NSmen and unit?
