This will be difficult to predict. The topic is so wide ranging. Many teachers can opt to go into different directions with essay questions for To Kill a Mockingbird. One potential essay topic that connects to some of the basic themes in the novel could center around justice. Perhaps, an essay question like this could be framed in the following way:
* How does Atticus define justice in To Kill a Mockingbird? Explain how he defines justice through both actions and through language. Given this construction of justice, how does it align with the definition through the tradition of American jurisprudence?
This type of essay question is built off of the theme of justice and fairness in the novel, and strikes at the essence of Atticus's characterization. At the same time, I would suggest that it is difficult because it forces the student to analyze the concept of justice in both the novel and in the modern setting.
Another essay question that can arise from the themes in Lee's novel could to analyze Atticus' parenting capacities. This essay question forces the student to analyze characterizations in light of larger themes. It is difficult because the student has to define the criteria for what it means to be a successful parent and apply those standards to Atticus. Specific situations and actions need to be recalled in order to test the validity of Atticus's parenting.
Finally, I would suggest that another essay question that is difficult is to analyze the different notions of Christianity that are displayed in the novel. How Christianity is shown is of vital importance to both Atticus's actions and the inertia that is set against him. The exploration of Christianity through quotes and actions of characters can illuminate behavior in the novel as well as thematic implications. Exploring how Christianity is used as a vehicle towards social justice as well as how it is used to perpetuate the Status Quo could be a very interesting and difficult essay question derived from the novel's themes.