Students read for the exam why they fail

Umh.. maybe they study in sort time. in my country there is a some special name for it SKS (sistem kebut semalam) -one night study. They study only one day before exam. Stuidy should continiuously. ^^ Or maybe they are nervous. If that so, all memorize lesson will gone from their brain But luck also effect here. not because some one didn;t past exam, prepare hard, and they still failed, it depend on luck. And not because they stupd or soimething