Read the last page of chapter 23. Jem thinks Scout’s words to the reflect her innocence and naiveté. How do her words also reflect her maturity?
I imagine you are referring to the section in which Scout says, "I think there's just one kind of folks. Folks" (227). In this section, she is responding to Jem's attempt to analyze and categorize people in a way he thinks is quite sophisticated. If you have an older sibling, or a younger one, it is likely that you have experienced this kind of "help" from your older sibling or have tried to instruct a younger sibling in a similar manner. (I was the big sister in my family.)
But Jem's analysis of "background" seems to be more a reflection of what adults believe, rather than something he has thought out for himself. Scout seems to have given the matter more thought and has considered the evidence in the world around her. She sees, for example, that Walter Cunningham is intelligent, but has not had the opportunities she and Jem have had. While she does not explicitly say so, we can infer that she believes in "nurture," rather than "nature," that the circumstances surrounding a person contribute more to a person's success than anything else.
While we have learned since this story was written that nature and nurture are both important, a recent book by Malcolm Gladwell, The Outliers, argues that accidents of birth can create more or less favorable environments for people, and that the world is divided into those who were the beneficiaries of those accidents or not the beneficiaries of those accidents.
Scout's opinion on this subject is intelligent, mature, and compassionate. And if we were to extend the story of Scout and Jem into some adult future, I would bet my money on Scout!