In the edition of Harper Lee's classic coming-of-age in the American South novel To Kill a Mockingbird consulted for this question, a link to which is provided below, the following quote is from page 83:

". . .the only time I ever heard Atticus speak sharply to anyone was when I once heard him say, “Sister, I do the best I can with them!” It had something to do with my going around in overalls. Aunt Alexandra was fanatical on the subject of my attire. I could not possibly hope to be a lady if I wore breeches; when I said I could do nothing in a dress, she said I wasn’t supposed to be doing things that required pants." [Emphasis added]

This quote, which is in Chapter Nine of Lee's novel, occurs in the context of Scout's discussion of family Christmases spent with her father's relatives, especially with Atticus' sister, Aunt Alexandra, who is a regular character throughout the novel. Alexandra is critical of the manner in which Atticus is raising his children, although she clearly loves and is devoted to her family. Scout, as Jean Louise Finch is called, is what back then would be commonly called a "tomboy," meaning a girl who enjoyed participating in activities traditionally associated with boys, such as contact sports. Today, of course, such antiquated notions of gender distinctions are no longer tolerated, but during the period in which To Kill a Mockingbird takes place, it was normal.