Erfworld isn't like that. Note that Wanda is able to cast an extremely powerful summoning spell that is WAY outside her speciality. While speaking to Sizemore she also says that she has little difficulty casting magic of any kind, but she simply has no interest in any school outside Croakamancy; this implies that the "schools" of magic you can cast in Erfworld come largely down to personality, not any intrinsic limitation of the magic itself.