The board shall cause all children over six (6) years of age in such asylum to be instructed in such branches of useful knowledge as may be suited to their years and capabilities, and cause the girls to be taught domestic vocations, such as sewing, mending, knitting, and housekeeping in all its departments. The boys shall be taught such useful trades as the board may direct. All children in such asylums, of sufficient age, shall be taught according to the course of the common schools.