Mrs. Henry made the threat to call the superintendent, though in my research to answer this question, I could not find a source to back up the previous answer. However, there is a lot to the story of Mrs. Henry and Ruby Bridges that not many people know. In light of the missing evidence for this answer, I will share some of that because it’s quite interesting.
Mrs. Henry was expecting to have a full classroom when she went to school that fateful day. She was told to return the next day and she’d have a student. A single student - Ruby Bridges. So, she returned, and met Ruby the next day. Instead of giving up (as it is suggested the school wanted her to in the face of the mobs), she continued to teach Ruby.