Over the past half-century, the amount of time college students actually study — read, write and otherwise prepare for class — has dwindled from 24 hours a week to about 15, survey data show. ...At Sweet Briar College, a private women’s school in Virginia, students reported 19 hours of study in an average week. Weekly study among seniors averaged 18 hours at St. Mary’s College of Maryland, 17 hours at the College of William and Mary, 16 at the universities of Maryland and Virginia and Catholic University, 15 at American University and 13 at Howard University.