The book "What Kathy Did at School" by Susan Coolidge is an exciting story about the adventures of Kathy Carr, who goes to school with her sister. At school, Katie faces new challenges, new friends, and learning that is often unexpected. She learns to make important choices and find solutions for various life situations. This book is not only an interesting story, but also important lessons about friendship, loyalty and self-improvement that will be useful for young readers.