As all experienced college teachers know. each class has its own particular dynamic its own collective personality, its own"chemistry Many of us who have been assigned to teach two sections of the same course in a given semester-using the same syllabus, the same books, the same lecture notes perhaps even the same room-have discovered that these"parallel" sections quickly become very different classes. Each individual student brings a complex mix of background variables to the course. The student's socioeconomic class, linguistic and cultural background, attitudes and values, level of general academic preparation, learning strategies and skills, and previous knowledge of the specific subject matter can all influence his or her performance in the course. As students interact in the classroom, the mixture of variables that can affect learning becomes vastly more complex. In addition, the instructor, the discipline, the organization of the course, the materials used, and even the time of day the class meets-all have an eftect on classroom learning