Maine’s first charter school is opening its doors. The Maine Academy of Natural Sciences at Good Will-Hinckley begins classes on Monday, making it the first charter school in the state’s history. The academic program uses hands-on methods focused on agriculture, forestry and environmental sciences. The idea is to tap the strengths of Good Will-Hinckley’s central Maine campus by using the forests, fields and farmland as classrooms and laboratories. School officials inked a five-year deal with the state charter commission on July 31. The school set a goal of enrolling 40 students this fall.