This study examined the interrelationships among three major components of classroom teaching: subject matter content knowledge, classroom management, and instructional practices. The study involved two middle school science classes of different achievement levels taught by the same female teacher. The teacher held an undergraduate degree with a major in social studies and a minor in mathematics and science from an elementary teacher education program. The findings indicated that the teacher's limited knowledge of science content and her strict classroom order resulted in heavy dependence on the textbook and students' individual activities (e.g., seatwork) and avoidance of whole-class activities (e.g., discussion) similarly in both classes. Implications for educational practices and further research are discussed.