Class size studies

Smaller classes help keep students focused, engaged
Students behave differently in smaller classes, staying on task with greater frequency and interacting more with their teachers, according to an analysis of research gathered from various countries, including the U.S. Small classes work for children, but that's less because of how teachers teach than because of what students feel they can do: Get more face time with their teacher, for instance, or work in small groups with classmates.
Peter Blatchford, P., Galton, M., University of Wisconsin-Madison. (2008). Class Size Effects: New Insights Into Classroom, School, and Policy Processes.
American Educational Research Association Annual conference, New York.
http://www.aera.net/meetings/Default.aspx?menu_id=342&id=4850