Why Teachers Matter

“Crowd Control” by Martin R. West and Ludger Woessmann, in Education Next (Summer 2003), 226 Littauer North Yard, 1875 Cambridge St., Cambridge, Mass. 02138–3001.

Reducing class size is an oft-recommended education reform, supposedly boosting student performance by letting teachers spend more time with individual pupils. In the 1999–2000 school year alone, states spent an estimated $2.3 billion to accomplish that. But an international comparison suggests that there’s an interesting twist to the remedy.

West, a research fellow at Harvard University, and Woessmann, a senior researcher at the Ifo Institute for Economic Research in Munich, Germany, used data from the Third International Mathematics and Science Study, conducted with middle-school students during 1994–95, to compare the effects of class size around the world. “While Americans squabble over whether class size should be 18 or 25 students,” they observe, “teachers in [South] Korean schools routinely face classrooms of more than 50 students.” In fact, the best-performing countries generally tended to have larger classes.

The researchers studied 18 countries, taking advantage of the natural variations in class size between grades to determine whether smaller was better. “We looked at whether seventh graders in a particular school performed better than the same school’s eighth graders (relative to the national average for their respective grades) when, on average, the seventh-grade classes were smaller than the eighth-grade classes.”

In only two of the 18 countries—Greece and Iceland—did smaller classes seem to improve student performance. The results in 12 of the remaining countries were statistically insignificant: Class size made no difference. In four others (including the United States), there wasn’t enough variation in class size from one grade to the next to produce a meaningful verdict.

In Greece and Iceland, however, the authors found “substantial” benefits from reducing class size: “Students scored just over two points higher for every one student fewer in their class.” Why? The difference may be in the quality of the teachers, West and Woessmann speculate. The two countries rank relatively low in per pupil spending and teacher salaries—and, presumably, in teacher quality. Apparently, better teachers can handle bigger classes. “Smaller classes appear to be beneficial,” the authors conclude, “only in countries where average teacher quality is low.”