During beta the only deck I got as a drop was quest reward in Marleybone. Otherwise I had to buy the decks at the deck shop for in game gold. The one in the hidden shop on Krokotopia (Mummified Deck) is a nice one but it is not school based.
I got a mummified deck in Krocktopia and three of the side quests in Marleybone Knights court gave me 3 decks but I couldn't use one(not my school) so I sold it. As for Moo Shu, I haven't been there yet. It can be luck such as pets or your willingness in the case of Marleybone to do other quests besides the main one.