The department, acting with the superintendent, shall, under a system of marks, or otherwise, fix upon a uniform plan by which girls may be paroled or discharged from the school, which system shall be subject to revision from time to time. Each girl shall be credited for personal demeanor, diligence in labor or study and for the results accomplished, and charged for derelictions, negligence or offense. The standing of each girl shall be made known to her as often as once a month.