Jenny's first weeks of kindergarten are full of challenges and disappointments. Her mother returns to nursing school and her father opens a part-time office at home; lively Jenny finds it hard to entertain herself while they're busy. Pleased at being termed ``rambunctious,'' she accepts her parents' offer of a gymnastics class, where an understanding teacher helps her overcome her reluctance to participate. She loses a tooth, ties her shoes, joins the first graders for reading, and finds a best friend, as she had eagerly anticipated. Then she's felled by chicken pox, just before a class trip and her birthday, but family and friends rally round for some satisfying surprises. A warm, humorous look at a delightful child who meets life head-on, occasionally with an Amelia Bedelia tilt; the supporting cast is also enjoyable. Pryor has a gift for relating an upbeat, credible story. Let's hope the intended audience is willing to read about a kindergartner. Illustrations not seen. (Fiction. 7- 11)