Teaching introductory classes at a university for even a few semesters makes most instructors aware of problems which are particularly common in these courses. Aside from the usual variety in student ability and interest, introcuctory students differ widely in their purpose for taking the courses and future aspirations in the area. The majority of introductory level students at liberal arts schools are non-majors and will have no formal academic contact with the discipline beyond the introductory course. Usually, they take the introductory course to fulfill some type of "general education" requirement. Hence, the population of the introductory class is particularly heterogeneous and the instructor is faced with the perennial problem of choosing a "level" at which to teach the course.
Winzenz, M., & Winzenz, D. (1988). Individualized Reading In a University Course. Reading Horizons, 28 (2). Retrieved from https://scholarworks.wmich.edu/reading_horizons/vol28/iss2/4