The Great Escape (S.O.S. Society of Substitutes, Bk. 1)

When Milton Worthy learns his classroom's pet ferret is the evil mastermind behind a dastardly plot for world domination, it's more than just about any kid could handle. But then not every kid is the son of a member of the super-secret, super awesome Society of Substitutes! Now it's up to Milton and his substitute-teacher mom to save Beacher Elementary School before it's too late.