Scout's descriptive narrative is quite thorough throughout the novel, but she gives the reader maddeningly little information about what she actually looks like. Scout is six years old when the story begins, and we can assume that she is big for her age since she is larger than most of the boys in the story. Even though Walter Cunningham Jr. is older, Jem tells us that
"You're bigger'n he is." (Chapter 3)
Cousin Francis is a year older than Scout, but she has no problem with him once she decides to "split my knuckle to the bone on his front teeth." Scout is much larger than Dill, who the children guess is only "four-and-a-half." And she is bigger than Little Chuck Little, "among the most diminutive of men." We do know that Scout prefers overalls and "breeches" to dresses and skirts, but she tells us little else about her actual appearance. In the movie adaptation, Scout is pictured with very short, dark hair, usually wearing overalls and a "wife-beater" undershirt or flannel shirt underneath.
Scout Finch (her birth name is "Jean Marie Finch") is not only the main character of the novel, but is also the narrator. The entire story is told from the perspective of a first grade girl.
This being said, there is very little revealed about Scout's actual appearance. There are two main reasons for this. First, because Scout is narrating, and she is only six years old, she doesn't see much of a reason to describe her appearance, probably. Second, Harper Lee as an author wants us to associate ourselves with Scout's beautiful innocence and see the world through the eyes of this child. As a result, and in order to connect us deeper with Scout, ALL OF US (both boys and girls, men and women) need to connect with her on some level. Hence the idea of Scout being a tomboy.
Interestingly enough, we learn the most about Scout's appearance through her interaction with her dreaded Aunt Alexandra. At least, we learn a lot about her clothes:
Aunt Alexandra was fanatical on the subject of my attire. I could not possible hope to be a lady if I wore breeches. 81
Therefore, we know that Scout wears "breeches" and "overalls" and the typical playclothes that a boy would wear. We are also told that she has straight bangs across her forehead; however, we are told this in a very indirect way. At one point, Boo Radley makes two tiny dolls for Scout and Jem. One is a boy and one is a girl. They are absolutely supposed to be representations of Scout and Jem. The little girl doll has bangs, and that is the only clue to Scout's hair.
Another thing we know about Scout is that she is bigger than the average first grader. She fights with the boys and Jem even admits that Scout is "bigger'n" other boys older than her.
This might seem a little bit silly, but it's also safe to assume that Scout has plenty of scars on her hands from punching boys in the face. She reveals the result of the altercation with Francis when she "split [her] knuckle to the bone" because she punched him in the teeth.
Thus, keep in mind that the question you have been asked to answer may be a "trick" question, with the answer being that there aren't really enough details to answer it properly. It may also be a method for a teacher to find out if the student only watched the movie instead of reading the book.