Jo King was a witch and a Gryffindor student at Hogwarts School of Witchcraft and Wizardry in the 1990s. Sometime in the 1990s, the library books Jo took out were overdue, and thus her name was included on a list of students with overdue books that was put up on the bulletin board in Gryffindor Tower by Madam Pince. She personally signed up to join the Hogwarts Gobstone Club on a sign-up sheet that was posted on the Gryffindor bulletin board. She also registered for a trip to Hogsmeade on another sign-up sheet posted on the Gryffindor bulletin board, which was scheduled for Saturday the 15th in an unknown month.