Large classes of 50-plus students were common in early 20th century schools, especially in cities.
Class size fell throughout the past century to around 30 students in elementary and secondary classrooms, dipping to 25 and rising to 35 in times of budgetary retrenchment. Beginning in the 1980s, state efforts to reduce class size to 20 students or less per classroom, especially in primary grades, led legislatures to fund smaller class size in order to lift student achievement. Research studies had established that smaller class sizes (numbers varied in these studies from 15 to 25 student) produced gains in test scores.
For example, in the Tennessee experiments in reduced class size in elementary schools—a small class was 13-17 students; a large class was 22-26 students—achievement test score gains did occur especially for low-income and minority children in primary grades. Most reduced-class size efforts before and after these studies, however, seldom reached the 13-17 students per teacher that Tennessee had created (Tennessee study five year follow-up).
The theory was that small class size would permit teachers to engage students more fully, use particular classroom practices such as small group and individual instruction more easily, and, as a consequence student academic performance on tests would improve. The theory had a few holes in it.
Researchers examined one of the largest efforts to cut class size in California in the mid-1990s. The state legislature invested $1 billion to downsize primary grade classes of around 30 students to about 20. Parents, teachers, and school boards applauded the effort and sang the praises of the legislature and governor. Note, however, that California created classes that were close to the “large” ones in the Tennessee experiment.
What did the researchers find after five years of reduced class size in California? (RAND report)
“We tracked achievement gains in cohorts of students with different amounts of exposure to CSR [class size reduction] from kindergarten through third grade. Whether we used statewide average scores or conducted a more refined school-level analysis we reached the same conclusion. We found no association between small differences in exposure to CSR (i.e., the total number of years a student had been in reduced size classes) and differences in academic achievement” (p. 15).
And what did researchers find about teaching practices in reduced size classes with about 20 students compared to larger classes? From self-reports of how teachers taught their lessons and direct observations of lessons, the researchers concluded that:
“For the most part, teachers in reduced and non-reduced size classes reported using selected instructional activities with equal frequency. In mathematics these activities included using a calculator, using mathematics in the context of other subjects, doing mathematics worksheets, using patterns to discover mathematical relationships, and practicing computational skills. In language arts, the activities included having guided discussion about reading, discussing new or difficult vocabulary, working in a reading book, and listening to the teacher read stories” (p.22).
Another researcher examined studies covering U.S. and international efforts to reduce class size since the 1970s, including the Tennessee and California studies noted above. He found very small effects on achievement and little to no change in classroom practices of teachers in “small” and “large” classes (see pp. 403-410). Even with all of the embellished talk from reformers about fundamentally altering classroom teaching, at best, there were only incremental changes in how teachers taught.
In short, smaller class sizes even in the range of 20 students in a class does not mean that teachers automatically shift to other forms of teaching. Yet, the fact remains that teachers, by and large, want smaller class size in the 20-25 student range because it is simply easier to manage behavior and differences among students in their motivation to learn, interests, and backgrounds. Teachers report that they can differentiate materials and activities with far less stress than in larger classes. Nonetheless, shifts in teaching practice, say from teacher-directed to student-centered happen infrequently as a result of smaller class size.