Classroom teaching is a nearly universal activity designed intentionally to help young people learn. It is the process that brings the curriculum into contact with the students and through which national, regional, or state education goals are to be achieved. It is reasonable to assume that teachers and teaching make a difference in students' learning. However, methodically studying the direct effects that teachers and teaching may have on student learning is difficult, though not impossible. The TIMSS 1999 Video Study is based on the premise that the more educators and researchers can learn about teaching as it is actually practiced, the more effectively educators can identify factors that might enhance student learning opportunities and, by extension, student achievement. By providing rich descriptions of what actually takes place in mathematics and science classrooms, the video study can contribute to further research into features of teaching that most influence students' learning.

Comparing teaching across cultures has additional advantages.

• Comparing teaching across cultures allows educators to examine their own teaching practices from a fresh perspective by widening the known possibilities. In addition to examining how teachers across one's own country approach mathematics, opening up the lens to include an examination of how teachers in another country approach the same topic can make one's own teaching practices more visible by contrast and therefore more open for reflection and improvement.



• Comparing teaching across cultures can reveal alternatives and stimulate discussion about the choices being made within a country. Although a variety of teaching practices can be found in a single country, it sometimes requires looking outside one's own culture to see something new and different. These observations, combined with carefully crafted follow-up research, can stimulate debate about the approaches that may make the most sense for achieving the learning goals defined within a country.

Using national video surveys to study teaching has special advantages.

• Video enables detailed examination of complex activities from different points of view. Video preserves classroom activity so it can be slowed down and viewed multiple times, by many people with different kinds of expertise, making possible detailed descriptions of many classroom lessons.



• Collecting a random national sample provides information about students' experiences across a range of conditions, rather than exceptional experiences only. The ability to generalize nationally can elevate policy discussions beyond the anecdotal. Therefore it is important to know what actual teaching looks like, on average, so that national discussions can focus on what most students experience.