1. She couldn't read. Scout was a bright child, but she hadn't learned to read yet. This made her a target for ridicule from the other children and her teacher, Miss Caroline.
2. She told on Walter Cunningham. When Walter, a poor farm boy, couldn't afford a lunch, Scout told Miss Caroline, leading to an embarrassing encounter with Walter's father. This showed Scout's naive understanding of social dynamics.
3. She fought with Jem. After being humiliated in class, Scout started a fight with Jem, showing her anger and frustration at her first day experiences.
These mistakes highlight Scout's innocence, her strong sense of justice, and her journey to understanding the complexities of the world around her.