Murals offer a quick and dirty way to introduce a school to the joys of mud. Unlike play sculptures and benches, they require no foundation, minimal prep, and not much mud, either. The typical approach to murals demands a narrative theme -- on my first one, I suggested "creation and the four elements" (we were working with earth, air, fire (sun), and water, after all...). It worked fine with the kids, who made something that looked much better than the industrial brick wall under it. Some parents got a bit worked up, but by the time I heard about it, a creative volunteer had welcomed . . .