Across the street from a leafy park, Boston's William E. Carter School, with its long and horizontal volume, colorful terra-cotta cladding, and an entrance defined by a welcoming cantilevered awning, emanates the kind of positive energy that every public school should project. “We had a captive audience,” says Patrick Cunningham, the project's design principal. “It was the one place that worked,” says school principal Mark O'Connor. Nearly all the Carter students use wheelchairs, so it is hardly surprising that the building's corridors, restrooms, and doorways are generously sized to meet mobility needs. Carter students have a high incidence of asthma, which is often exacerbated by such indoor air pollutants, points out Cunningham.