From The Washington Post: A Loudoun County (Va.) developer is putting 10 acres of land in Purcellville into a conservation easement to protect in from development so that a teacher at Loudoun Valley High School can continue to use it as an outdoor classroom. John DeMary and his students have been erecting footbridges and laying sawdust over a trail they cleared on the land, which includes one of the few remaining stands of old-growth forest in the area.