In conversational sentences that convey a kid's side of the fence and facing paintings with the bite of a thirties' protest poster is a chronicle that could be a folk ballad. The trouble started because there wasn't any place to play: cars in the street. ""No handball against that wall,"" too much noise in the hall. The lot vacated by a demolished tenement seemed okay until some visiting ladies call it a mess. The Mayor's promise to clean up brings around a pile of dirt, and the kids go to it sitting on top as President pro tem, staging a funeral for a dead pigeon, sliding down in winter, painting trees to match the grass in spring. But the beautifying people know a mistake when they see one; that dirt belongs elsewhere. Or does it? the kids protest and the neighbors back them up. So the RFK-haired, Lindsay-jawed mayor compromises: the dirt can stay in a corner, the rest will be a conventional playground. ""We sure needed that park. But sometimes. . . I pretend it's the way it used to be, just a big pile of dirt in the middle of an empty lot."" Honest and big-city soluble, with a vocabulary for third graders, a concept mature enough for older slow readers.