Perhaps the most heroic traits displayed by the three children in To Kill a Mockingbird are their abilities to maintain their own personal integrity in the midst of all the hypocrisy that surrounds them. They manage to see through the gossip and innuendo about Boo Radley, recognizing that he is a friendly neighbor rather than a nocturnal ghoul. Unlike the jury, they look past his skin color and see that Tom is an innocent man, physically incapable of beating or raping Mayella Ewell.
They perform heroic deeds on their own as well. All three come to Atticus' rescue at the jail, and Scout's innocent conversation with Mr. Cunningham turns the tables on the prospective lynch mob. Dill's quick thinking in creating his story about playing "strip poker" saves Jem and Scout from getting in trouble with Atticus. Jem comes to the rescue of Scout, trying his best to fight off Bob Ewell during their walk home after the Halloween pageant.
They could be heroes because of their childish innocence. They aren't prejudiced or biased like everyone else. They view everyone as equals and believe that everyone should be treated fairly. Everyone else should be looking up to these children and ought not to be blinded by racism and wordly views.