professional organizations in the U.S.,22 compare with the role of those produced by official government agencies in other countries? The TIMSS data offer an unparalleled opportunity to learn how curriculum is directed and organized in a wide variety of countries. Analyses of these data also will allow probing of the concept of "national curriculum," its essential elements, and factors that influence its nature and functions in different cultural and political contexts.
• What is the role of the teacher, and how do teachers learn to do what they do?
Looking at instructional practice across such a wide diversity of cultural contexts raises questions about teachers and the work of teaching. It will important to probe beneath the surface similarities and differences in teachers' roles in different contexts, to find out who teachers are, and to examine how they learn and develop their practice. What are the opportunities and conditions that contribute to what teachers do? In what ways do teachers' opportunities and conditions need to be considered when we look at instructional practices in other countries? How might these issues inform teacher preparation and professional development programs? Understanding of these issues is crucial in considering adaptation of practices across cultural settings.
• How do differences in educational practice among countries affect students?
On one hand, examining variations in intended and instructional practice is interesting. Much can be learned about the multiple forms that education can take across countries. On the other hand, the critical questions center on how these different approaches to curriculum and instruction affect educational outcomes, specifically student performance. For example, the six SMSO countries allocate substantially different amounts of time to particular topics, and their curricula reflect great variation in the number of topics intended for students to learn at each grade. These findings lead to questions about whether and how such practices may affect student achievement. How do students fare in systems that cover fewer topics per year? How does this curricular stance affect the thinking and practice of teachers? The TIMSS data not only have the potential to provide portraits of topic coverage across countries but also may afford an important opportunity to analyze the relations between the depth or breadth of the curriculum and what students learn.
What patterns or relationships can be unearthed in these vast data sets that offer insights into what affects what students learn? The SMSO report underscores the fact that what can be learned from TIMSS will depend on developing methods of analysis that maintain a serious respect for the complexity of ideas such as "curriculum," "instruction," and "culture" and that do not seek simplistic relationships among what are complicated elements and interconnections.