What Katy Did at School is the second novel in the series. The book follows Katy as she attends a boarding school with her sister Clover where they befriend an adventurous girl named Rose Red. Sarah Chauncey Woolsey, who wrote under the pen name Susan Coolidge, was a prolific children's author. Coolidge is now most famous for writing the classic coming of age stories featuring Katy Carr and her family. The books are considered semi-autobiographical as Katy Carr is based off of Coolidge's childhood and Katy's siblings are based off of Coolidge's brothers and sisters.