A preschool that opened in Centennial last spring soon will hold its first open house for potential student families. Such events are common during this time of year as parents look for the best place to enroll their children. But Joshua Academy, as the school is named, presents an uncommon opportunity for its pupils: It teaches children with autism and other developmental disabilities alongside what staff call “typical kids,” presenting all with a curriculum centered on literacy and arithmetic as well as empathy, kindness and social and emotional growth.