Scout is looking forward to school because she is sick of watching Jem run around on the playground with his friends while she stays at home. Scout is anxious about going to school and meeting new friends. During the school year, Scout is lonely at home and wants play with the kids in her community the way that Jem does. At the beginning of Chapter 2, Scout mentions that Dill has left for the summer, and she longs to join the children on the playground. She recalls all the winter days that she sat in her tree house and watched Jem on the playground with his friends. Also, Scout is a naturally curious, intelligent girl who seems like she would enjoy school. Unfortunately, Scout has a rough first day of school and ends up not wanting to go back.

Scout, whose real name is Jean Louise Finch, is the young daughter of Atticus in To Kill A Mockingbird. She is the adult narrator, recalling events from her childhood and recalling what an opinionated little girl she was who would prefer to settle her disputes using her fists, much to her father;s dismay. Atticus tries to instill respect and tolerance in his children, encouraging them to never judge someone until "you climb into his skin and walk around in it." Atticus has also taught Scout to read, and, she is initially excited to go to school and no longer to have to watch the school children from her tree house. Now she can accompany her brother, Jem.  

However, school is a huge disappointment and, in fact, an embarrassment, for Scout who, in an attempt to help Walter Cunningham. tells her teacher, Miss Caroline, that she should not offer to loan Walter money to buy lunch because he will refuse to take it and cannot accept her offer as he is too poor to pay her back. Scout gets into trouble with her teacher over Walter and is even smacked with a ruler, ruining her first day. Her problems are intensified because  Miss Caroline has discovered that Scout has already learned to read, a fact which, rather than impressing the teacher, causes her to suggest that Atticus has taught Scout incorrectly and that everything will have to be re-learnt:

she said you taught me all wrong, so we can’t ever read anymore, ever." 

Scout loves to improve her mind, and she has always been ahead of others in terms of academics, due largely to her fathers tutoring. Scout has a proactive nature, and knows that knowledge is important. Her father is a learned man-and Scout wishes to be like him, in the end.

Scout loves learning and wants to go to school to show off her skills in reading and to learn more.

She is shamed by her teacher who doesn't like the fact that Scout already knows how to read, and who tells her that Atticus has no business teaching people.

I assume that you are asking about the part at the very beginning of Chapter 2.  At that point, Scout says that she had never looked forward to something more than she was looking forward to school.

Although she does not exactly say why she is looking forward to school, it would appear that she is eager to go so that she could play with Jem and the other kids.  She does not say anything about wanting to learn -- she just talks about how she watched them play their games and how she wanted to join them.