Changeling is a novel written by Molly Harper. It was first published in 2018.
If 14-year-old Cassandra Reed makes it through her first day at Miss Castwell's Institute for the Magical Instruction of Young Ladies without anyone discovering her secret, maybe, just maybe, she'll let herself believe that she really does belong at Miss Castwell's.
Except Cassandra Reed's real name is Sarah Smith and up until now, she lived her whole life in the Warren, serving a magical family, the Winters, as all non-magical "Snipes" are bound by magical Guardian law to do. That is, until one day, Sarah accidentally levitates Mrs. Winter's favorite vase in the parlor...
But Snipes aren't supposed to have magical powers... and the existence of a magical Snipe threatens the world order dictated during the Guardians' Restoration years ago. If she wants to keep her family safe and protect her own skin, Sarah must figure out how to fit into posh Guardian society, master her newfound magical powers and discover the truth about how an ordinary girl can become magical.