I would like to say "no" because a spell doesn't have a school or subtype until it is revealed... but that would directly go against several counterexamples (e.g. how [mwcard=FWQ09]Sectarus, Dark Rune Sword[/mwcard] can only cast
curse enchantments, and how [mwcard=MWSTX2FFC11]Sersiryx, Imp Familiar[/mwcard] ups the specific conditions on a face-down enchantment by only being able to cast level 1-2
curse enchantments). So... I guess yes (?), you can claim a facedown Enchantment is a certain level, has a certain subtype, or belongs to a certain school.