Höhenfeuer (1985)

A year on an Alpine farm: an older couple have two children, Belli, who wanted to be a teacher, and the younger Franzi, deaf, and although he works like a man, child-like. Belli teaches him. In his work, he can become frustrated, so when he throws an expensive mower over a cliff in a fit of pique, his father banishes him to the outskirts of the farm, where he uses pubescent energy to break rocks and build walls and cairns. (It's the tradition of the father's family, called "The Irascibles" by neighbors, to spend puberty doing this.) Belli visits him and they begin sleeping together. By winter, the boy is back in the house and Belli is pregnant. Soon her parents must know.