Two main kinds of data were collected in the video study: videotapes and questionnaire responses. We also collected supplementary materials (e.g., copies of textbook pages or worksheets) deemed helpful for understanding the lesson. Each classroom was videotaped once, on a date convenient for the teacher. One complete lesson—as defined by the teacher—was videotaped in each classroom. A primary purpose of the questionnaire was to get teachers’ judgments of how typical the videotaped lesson was compared to what we would normally see in their classroom.

Teachers were initially contacted by a project coordinator in each country who explained the goals of the study and scheduled the date and time for videotaping. Because teachers knew when the taping was to take place, we knew they might attempt to prepare in some way for the event. In order to mitigate any bias that might be caused by their preparation, we gave teachers in each country a common set of instructions. We told teachers that our goal was to see what typically happens in the mathematics classrooms of their country, so that we really wanted to see exactly what they would have done had we not been videotaping.