By Jay Mathews
Washington Post Staff Writer
Monday, March 10, 2008
For 20 years, a large study of class size in Tennessee, known as Project STAR, has raised hopes that reducing the number of children in inner-city classrooms to 17 or fewer would yield significant increases in achievement. It was by far the most authoritative finding in favor of reducing class size and was generally considered one of the most important educational studies of its time.
But a Northwestern University researcher, looking closely at the same data on thousands of students from kindergarten through third grade in 79 schools, has concluded that high achievers benefited more from the small classes than low achievers. Since low-income students in urban neighborhoods have lower achievement, on average, than students from more affluent families, the finding in the March issue of Elementary School Journal contradicts assumptions that class size reduction might have a significant effect on the gap between rich and poor students.
"While decreasing class size may increase achievement on average for all types of students, it does not appear to reduce the achievement gap within a class," Spyros Konstantopoulos, assistant professor at Northwestern's School of Education and Social Policy, said in a statement released by the university.
The $3 million Project STAR study was launched in 1985. It was unusual for the large size of the sample of students, for the long, four-year period in which their progress was recorded and for the random assignment of students to three kinds of classes -- small (13 to 17 students per teacher), regular (22 to 25 per teacher) and regular with aide (22 to 25 students with teacher and full-time aide). Classroom teachers were also randomly assigned, giving the study a scientific validity rarely found in educational research.
Several researchers concluded that the results left no doubt that small classes had an advantage over larger classes in primary-grade reading and math. "Given that class size reduction is an intervention that benefits all students, it's tempting to expect that it also will reduce the achievement gap," Konstantopoulos said. Previous reviews of the data, however, provided weak or no evidence that lower-achieving students benefited more than others, and his study, he said, buttressed those findings.