Her articles and book reviews have appeared in The Washington Post, the St. Louis Post Dispatch, Scholastic News, Cobblestone, and The Five Owls. She is also a contributor to the Dorling Kindersley Eyewitness Travel Guides. She often writes on issues related to social justice: Her books include Refugees: Seeking a Safe Haven, The Underground Railroad in American History, Freedom Calls: Journey of a Slave Girl, Lucretia Mott: Friend of Justice, and Harriet Tubman. She is a member of the Society of Children’s Book Writers and Illustrators (SCBWI) and the Children's Book Guild.
A graduate of Yale University, Kem majored in English and French. She was a teacher for many years—she has taught writing in the BFA program at the Corcoran College of Art + Design, English and drama in high school, and creative dramatics in elementary schools. She was also the editor of The Learning Center Newsletter.