Few high schools, let alone those in cities, have hens, pigs, and sheep, a one-acre vegetable garden, or an extensive network of hiking trails. But Common Ground, in New Haven, Connecticut, is far from ordinary. The mission of this 200-student charter high school, which sits at the edge of a wooded, 1,800-acre state park, “is to instill environmental literacy in urban kids,” says Melissa Spear, executive director.

Since 1997, when the school was founded, Common Ground has expanded several times, always by adding onto its base of operations—a barnlike, wood clapboard structure referred to as the hilltop building because of its location on the steeply sloping campus. But about eight years ago, with its student body still growing, and with more summer, after-school, and community programs run by its parent nonprofit, Common Ground’s management team and board began to consider another expansion, issuing a request for proposals in 2011.

Gray Organschi Architecture, a New Haven– based firm known for its attention to craft, decided to compete for the project because of an affinity for the school’s educational vision. “Common Ground’s values were close to home,” says principal Alan Organschi. Although several firms that specialize in K–12 construction were also in the running, the selection committee chose Gray Organschi, in large part because of its encompassing view of environmentally responsible design. “Their interest in sustainability goes beyond merely reducing operational energy,” says Spear. “They also consider the materials and where they come from.”

These ideas are manifest in the rustic, almost 15,000-square-foot, two-story building, completed last April. Behind its cedar rainscreen skin and below its irregular sawtooth roof, the new $9.3 million structure houses a small gym that also serves as an event space, classrooms for science and art, and offices. The new facility is positioned near the base of the school’s site, with its second floor connected to the upper part of campus and the hilltop building by a pedestrian bridge.

Arguably the new building’s most remarkable feature is its structure, which consists primarily of exposed black spruce, with glulam trusses and beams, and cross-laminated timber (CLT) used for bearing and shear walls and a stressed-skin roof system. CLT, which is not yet common in the U.S., is made of multiple layers of dimensional lumber to form large, slablike panels. A sturdy-looking but sleek central stair is also constructed of this material.

Although these wood components are highly engineered, they retain the evidence of their natural origins. With knots, the direction of the grain, and the individual pieces of lumber easily discernible, they lend the interior a tough, vaguely Scandinavian feel. And from an environmental standpoint, this use of mass timber, instead of steel or concrete, means that the building sequesters, rather than emits, carbon. According to Gray Organschi’s estimates, it offsets 447 metric tons of carbon dioxide, the equivalent of the annual emissions of 95 cars.

The method of construction was also environmentally sound, with the wood manufactured into CLT and glulam in northern Quebec, near where it was harvested. The glulam and CLT material was then fabricated into elements, including trusses, stair components, and insulated roof panels, in a New Hampshire factory. The approach minimized disruption to the site and meant that, once the foundations were poured, the structure could be erected and enclosed by a crew of five workers equipped only with light tools and a mobile crane in about five weeks, says Organschi.

In addition to their environmental and construction benefits, the legible structure and its timber components help support the school’s educational goals. The students study the materials, devising their own tests to explain their physical and chemical properties. Hector Roman, a junior considering a career as a mechanical engineer, explains that the CLT is stronger than steel because it is made of several layers of wood from fast-growing trees. The pedagogical approach resonates, explains Emily Schmidt, the school’s chemistry and physics teacher, because “it introduces the science to the students in a way that is relevant to them.”

The students can talk at length about other features of the project, including its system of geothermal wells, the acoustical and thermal properties of the building enclosure, and how the surrounding bioswales and wetlands clean the rainwater that runs off the standing-seam roof. But when the young occupants are asked about their favorite features, they invariably point to experiential aspects rather than environmentally beneficial or functional attributes. Hope Dymond, a high school junior, points to the quality of the light that comes in through the north-facing clerestory windows and the glimpses of the sky they afford.

Such comments point to the real triumph of the project. The building is a genuinely handsome expression of the values of the school in built form, as well as an instructional tool. But it is also a great environment for teaching and learning—and for contemplating the clouds.