"HOW STUDENTS LEARN" - A Study in the Field of "Individual Behavior"

Although the definition of learning and the theories of "how students learn" have been thoroughly studied, a new field has arisen in the study of "individual behavior" and how students who seem the same academically actually come to the first day of class with far differing personal credentials.Does "college ready" mean academically or should it also include socially and emotionally?All the students in their first day as freshmen, have been accepted to the university and have passed the entrance requirements whatever they may be.They have at least the minimum SAT score requirement and sometimes further requirements such as a portfolio.So why is it, four years later, about one third to one half of these students actually graduate?