Common themes that exist between To Kill A Mockingbird and The Help can be seen in how both address racism and the role of the individual.
The theme of intolerance is a critical element to both works. Maycomb embodies institutional and social discrimination. The majority of Maycomb society willingly accept and perpetuate social stratification. Atticus has to encounter this in how he wishes to raise his children and his defense of Tom Robinson. While much of this is racial, the demonizing of Boo Radley is another example of how the theme of intolerance permeates the work. The presence of discrimination is a critical element to Stockett's work, as well. Skeeter, Aibileen, and Minnie must confront the embedded racism which is a part of Jackson. In writing the book, all three recognize the role they play in stopping a social ill hurting so many people. The theme of racism and discrimination on social and personal levels drives both narratives.
Along these lines, both works affirm the role of the individual in challenging such a reality. Harper Lee does not show a world where people are powerless. Atticus Finch becomes the sterling example of how agency can be used to challenge prevailing social attitudes. Even though Calpurnia sees the destructive effects of discrimination in a first hand manner, she does not stop in teaching Jem and Scout lessons about how all people must be treated with respect. When Scout realizes that there's "just folks" in the world and the need to treat human beings with dignity is critical, it underscores the theme of how people have power even in the face of overwhelming social inertia.
In The Help, Stockett shows that Skeeter, Minnie, and Aibileen all hold power in writing their book. They are not voiceless, and their strength is confirmed when they are able to convince more maids to join in the writing. At the same time, Aibileen leaves her position as a member of the help to do something else with her life. She might be old and the weight of the future might be a great deal to bear, but she has the ability to take action. Both works show how human beings can be the force of change. While it will be difficult, it is a goal worthy of embracing.