Helen Lester, , illus. by Lynn Munsinger. . Houghton/Lorraine, $15 (32pp) ISBN 978-0-618-10857-2

These propitiously paired collaborators (Hooway for Wodney Wat; Tacky the Penguin) again turn out a comic caper with a subtly delivered moral. Words and pictures set the scene with laugh-out-loud humor as readers meet the pajama-clad, somnambulistic students at Sleepy Valley Sloth School, which is perched on the branches of a tree. "Once in a while the teacher would remember his job and wake up with a lesson" in such demanding subjects as yawning, snoring and rolling over—but most of the time "the class just slept." Instead of lunch hour there are "lunch three hours," followed by naptime, study hall (when the sloths fall asleep in a hammock or on the floor, their books covering their faces) and recess (which finds the classmates draped over a swing set, dozing). The dismissal bell rings at 3:00, yet it takes them until dusk to exit (the custodian finally sweeps them out with a broom). Enter Sparky, whose energy and spunk her new classmates find anything but contagious. However, when an inspector comes from the S.O.S. (Society for Organizing Sameness) in the Mammal District and threatens to close down the school, the sloths follow Sparky's cues to successfully perform the required tasks—in such a way that they save their school without betraying their true nature. Score another one for Lester and Munsinger. Readers will hope the sloths return for a rematch. Ages 4-8. (Sept.)