Education in States and Nations: 1991
In addition to differing beliefs about "what works" best, the instructional practices employed by teachers can be influenced by cultural, social, demographic, and financial circumstances. Here we are able to present three roughly comparable measures - the percentage of school administrators who report assigning students to mathematics classes based on ability, the percentage of students reporting that they work in small groups in math class at least once per week, and the percentage of students reporting that they take a math test or quiz at least weekly. Student data for the second and third measures are based on responses by 13-year-olds in other countries and public school 8th-graders in the United States.
Note on interpretation:
To a great extent, assigning students to classes based on ability is only possible in larger schools, and the greater prevalence of ability grouping in the United States may be due, at least in part, to its larger average school sizes. Smaller schools can find it difficult simply to mass enough students to form grade levels, much less ability groups within grade levels. Many other countries, moreover, offer parents and students more choice in the school they can attend, thus giving them the opportunity to "ability group" themselves by school. The differentiation that occurs in many other countries among academic, vocational, and other tracks starting at the lower secondary level might be considered yet another form of ability grouping, again, between schools rather than within schools.