* The Teacher's Prejudice: Miss Caroline, Scout's teacher, is prejudiced against Scout's family and their way of life. She doesn't understand Scout's knowledge of the world, especially about reading and writing. This causes a conflict between them, making Scout feel belittled and frustrated.
* The Lack of Intellectual Stimulation: Scout finds the lessons boring and repetitive. She's already learned much from her father, Atticus, and feels the curriculum is below her intellectual level. This lack of challenge makes her feel bored and stifled.
* The Social Hierarchy: The school system reflects the rigid social hierarchy of Maycomb. Scout sees the differences in treatment between her and the other children based on their social standing, which she finds unfair and confusing.
* The Absence of Friendship: Scout struggles to make friends at school. The other children, like Walter Cunningham, don't share her interests or experiences. This isolation and lack of connection further contributes to her disappointment.
Overall, Scout's first day of school in "To Kill a Mockingbird" is a disappointing experience because of the clash between her independent spirit and the constraints of the school system.