How are Scout and Jem open minded in To Kill a Mockingbird?

The open-mindedness of Scout and Jem has been instilled by their father, Atticus Finch, who advises them to understand a person by "consider[ing] things from his point of view." Atticus also conveys his open-mindedness to his children by prohibiting Scout and Jem from antagonizing Boo Radley, or criticizing those the children may find different from themselves. Atticus seems determined to encourage both to retain the innocent view of life and people that often accompanies youth, without succumbing to prejudices and falsehoods. 

When the innocence of Scout and Jem is challenged by some of the harsh realities of life in Maycomb, Alabama, Atticus and others, like Calpurnia, Miss Maudie, and Dolphus Raymond, are often available to help the children navigate the tangled thoughts and emotions that darken their experience.

Jem is infuriated by the town's attitude towards Tom Robinson and is crushed when the jury finds Robinson guilty of the charge of raping Mayella Ewell. Unlike the majority of townspeople who routinely take the side of a white person against that of a black person, Jem rages against the prejudice of the people of Maycomb, whom he believes are content to send an innocent black man to die for something he didn't even commit:

"I always thought Maycomb folks were the best folks in the world, least that's what they seemed like."

Scout, though her path to tolerance is smoothed repeatedly by Atticus, comes to put aside many of her prejudices against the likes of Boo Radley, poor souls like Walter Cunningham, and even some of the irritating and eccentric ladies of the town, and learns to take to heart Atticus' advice to understand a person through by "climb[ing] into his skin and walk[ing] around in it."

While both benefit from the natural openness of youth, Scout's and Jem's open-mindedness is hard won. While Jem's may spring from his position as the older sibling better able to understand Atticus' moral (and legal) expositions, Scout's seems to come from the loving discipline her father shows her.