If, as it seems to be indicated, the essay needs to be concerned about actions limited from Chapters 1 to 3, then perhaps you can develop what Scout herself says:
Atticus said I learned many things today, and Miss Caroline had learned several things herself.
Scout continues, declaring that Miss Caroline has learned not to hand something to a Cunningham--which Scout tried to tell her. But, Scout reflects, had she been Miss Caroline, she would not have known not to do what she did.
So, reviewing the first day of school from inside the skin of Miss Caroline presents several obstacles: She does not know anyone, she knows nothing about their way of life, and she is new at teaching.
Placing the focus of your essay on being inside Miss Caroline's skin, as Atticus's metaphor describes taking on a different perspective, may be the direction in which to go since supporting details can be gleaned from the chapters previous to Chapter Three.