Boomer, a shaggy golden retriever and hero of Boomer's Big Day (1994, not reviewed), goes to school with his owner; after a morning of playing with the kids and then eating lunch (theirs), he becomes the star of the afternoon show-and-tell. McGeorge has skillfully blown up one incident into an entire book, with a well-timed text that offers a dog's version of events in school: ``A loud bell rang. A grown-up started talking. Everyone sat down and listened.'' Much of the humor arises from the matter- of-fact text and unexpected events in the pictures: In the scene of ``pictures to paint,'' paw prints in bright colors trail across paper and floor, and in the illustration of ``games to play,'' Boomer is seen stealing the soccer ball and disrupting the action. Whyte's tricks with point of view make ordinary classroom scenes fresh, e.g., she shows the arrival of children at school from high overhead and a close-up of clapping hands at Boomer's big moment. He's an endearing hero, just right for preschoolers curious about where their older siblings go during the day. (Picture book. 2-6)