I wouldn't classify Scout as biased, at least not in the traditional sense. She has been raised in a Southern town with lots of racist attitudes, but her father is quick to lovingly guide her when her own thoughts begin to reflect the predominant sentiments of the town.

In chapter 9, Francis calls Atticus a "nigger-lover," and Scout doesn't like it. She tells Francis to "cut it out" even though she also acknowledges that she doesn't know what he's talking about.

In matters of socioeconomic stratification, Scout sees things matter-of-factly. Some of the students in her class can afford lunch and some cannot. When she tries to explain this to her teacher (which admittedly could have been a private conversation), her efforts are interpreted as insulting. Later when her aunt makes disparaging comments about the Cunningham family by calling them "trash," Scout understands that there is a difference between the Ewells and the Cunninghams and that money isn't the determining factor. She later reflects on this as she talks things over with Jem: "That Walter’s as smart as he can be, he just gets held back sometimes because he has to stay out and help his daddy. Nothin’s wrong with him. Naw, Jem, I think there’s just one kind of folks. Folks.”

When Aunt Alexandra invites the missionary circle over, Scout is faced with a world she doesn't fully understand. One one hand, the women are meeting to discuss Christian love; on the other, Mrs. Merriweather complains that having "a sulky darky" around just ruins her day. The conversation spirals downward with the women noting that no one is safe in town after the Tom Robinson trial and that whites who try to help blacks are "misguided." Scout makes a mental reflection that she "wished [she] was the Governor of Alabama for one day: [She’d] let Tom Robinson go so quick the Missionary Society wouldn’t have time to catch its breath."

It is easy to forget how young Scout is. When the novel begins, she's around six years old and is only around eight when it ends. She hasn't developed the complex understanding of the world to hold her own biases but instead sometimes parrots the words she hears others saying, even if she doesn't understand them. Scout is precocious and forthright, but she is about as unbiased a narrator as you can find—which is one of the reasons that her perspective in the events of the novel ring with such truth.