Why do teachers today teach as they do, and why has teaching evolved in the way that it has evolved? In order to improve teaching, it is important to understand why teaching looks the way that it now does and how its general form can be explained. One way to address this question is at the classroom level. In this article we build on ethnographic research by using the 1999 Third International Mathematics and Science Study (TIMSS) video archives. Here we consider two possible explanations for the general patterns that have developed in school teaching. One explanation is that there are universal elements in most schools today that shape teaching practice. A second explanation is that countries have shaped teaching by evolving classroom methods that are aligned with their national cultural beliefs, expectations, and values. These would include beliefs about the nature of a subject and how students learn, expectations about the level of performance students should demonstrate, and the values held for school processes and outcomes.