Scout's excitement over her impending first day of school was shattered by the standoffish and pompous behavior of her first grade teacher, Miss Caroline. A first-year teacher and newcomer to Maycomb, Miss Caroline was in dire need of a few lessons concerning the people and ways of the town. On her first day, she insulted Scout's learning and Atticus' teaching skills; she paddled Scout's hands; she embarrassed Walter Cunningham Jr.; and she nearly provoked Burris Ewell into attacking her. Scout later managed to feel a bit of pity for Miss Caroline when she saw her weeping into her hands, for "she was a pretty little thing."
This question can be answered through a close reading of chapter two. In the first part of that chapter, we learn that Scout's teacher's name is Miss Caroline Fisher. She is a very young and rather naive teacher, especially when it comes to the inner workings of Maycomb's social networks. Scout tries to inform her of the in's and out's of Maycomb and the different families, but just ends up getting in trouble. The first day, Scout spends most of the time in the corner on a time-out, after a slap on the hand with a ruler. Miss Caroline will have to learn quite a bit in order to more effectively rule her little class, and the first day is quite an eye-opening experience for her. I hope that helped; good luck!