PE lessons must be a breeze for these kids after their walk to school — across a cliff face. For an hour, pupils as young as six edge along a crumbling 2ft-wide path cut into the rock up a mountain as an irrigation ditch. There is a safer route but it takes twice as long. Walking home too, the kids at Banpo school in Guizhou, China, have learned the high road tops the slow road.      –GN