Mr. Keesing, the author’s mathematics teacher, was annoyed with Anne Frank because she was very talkative in class. Despite repeated warnings, Anne could not control her habit of talking too much with her classmates. This constant distraction disturbed the class and irritated Mr. Keesing.
As a punishment for her excessive talking, he gave her extra homework assignments such as writing essays on the subject of “A Chatterbox.” Even after completing those, Anne continued to talk, which further tested Mr. Keesing’s patience. His annoyance reflected his strict and disciplined approach towards teaching, where he expected full concentration and obedience from his students.