Scout is presented as the opposite of a Southern belle in To Kill A Mockingbird. Although Aunt Alexandria wants Scout to be like her, Scout still takes after her father, Atticus. We can pretty much predict what Scout will be like when she's older. She doesn't carry the racism and double standards that the rest of Maycomb carries. Although she is very much like Atticus and has a lot of the same qualities as him she isn't as mellow. She is a very intelligent and confident tomboy.
In the book you find out that Atticus get criticized for the way he raises Jem and Scout. One of the big things he gets beef for is the way Scout acts. Scout dresses in overalls and climbs trees with Jem and Dill. I think she does this because it's either hanging out with Jem and do the things he does or play with herself.
I don't think that is the major reason she is a tomboy, I think like most younger siblings she looks up to Jem and wants to be like him. She also has this wild imagination that she could not satisfy with just dolls and tea parties. She is very adventurous and if she acted like a proper southern girl then she wouldn't be able to be adventurous.
When you begin reading the book you can tell that Scout is the way she is because of Atticus and how he raised her. Atticus taught Scout how to read before she even went to school. Scout and Atticus read the paper every night and it's their way of bonding. Scout is very intelligent for a six year old. Her vocabulary is just as good as any teenager these days. She understands what's going on. She may not understand...