Citizens for KPS

One anti-millage renewal website recently posted the following statement by one of their readers:

“[T]here is no evidence that spending more money makes schools stronger.”

This is a commonly held belief. However, the research evidence does not support this belief. More spending on schools, if that spending is focused on the classroom, has been found by rigorous research to significantly improve student achievement.

The best recent review of the research on school resources and student achievement is by Alan Krueger, Professor of Economics at Princeton, in a paper entitled “Economic Considerations and Class Size”. http://www.irs.princeton.edu/pubs/pdfs/447.pdf . (This link is to a free working paper version of this paper; the paper has since been published in the Economic Journal.) Class size, or pupil-teacher ratio, is one of the most important factors in determining school district spending per student. In addition, class size is easier to measure in similar ways across different school districts than is the case for other school spending variables, which may be reported in different ways across districts or certainly across states.

What Professor Krueger finds, in reviewing 59 studies of the effects of class size on student achievement, is that although these studies include a wide variety of results, the average effect of lower class size on student achievement, if all studies are given “one vote”, is to significantly increase student achievement. There are almost twice as many studies that find that lower class size has significant positive effects on student achievement, compared to studies finding that lower class size has significant negative effects on student achievement. The effects of lower class size in improving student achievement become even stronger when we place greater weight on studies that appeared in more highly regarded academic journals.

More importantly, the most rigorous scientific study of the effect of class size on student achievement finds effects that are statistically significant and large. Only one study, Project STAR, has randomly assigned both students and teachers to large and small class sizes, and then followed students to see what effects different class size has on student achievement.  Students were randomly assigned to class sizes during grades K-3 that averaged 15 students per teacher for the “treatment group”, and averaged 22 students per teacher for the “control group”.

A random assignment experiment has some significant methodological advantages over the usual social science study that attempts to estimate the “effect” of lower class size. In the usual social science study, lower class size is not randomly assigned to students. Lower class size may occur for many reasons that may bias the estimates. For example, if the government tries to make class size lower for schools or school districts with many students from low-income families, then students with lower class size will tend to come from families with lower incomes. Because lower family income is associated on average with lower test scores, this correlation may make it appear that lower class size is “causing” lower test scores, which is a mistaken inference. In contrast, in a random assignment experiment such as Project Star, because students and teachers are randomly assigned to different class sizes, there will on average be no expected difference between students in low class sizes, and students in higher class sizes, except for the class size difference.

The best recent summary of the evidence from Project Star is a paper by Diane Whitmore Schanzenbach, an assistant Professor at the public policy school at the University of Chicago, entitled “What Have Researchers Learned from Project STAR?” The paper is available at http://harrisschool.uchicago.edu/About/publications/working-papers/pdf/w... .(This link is to the working paper version of the paper; the paper has since been published in Brookings Papers on Education Policy.)  

What Professor Schanzenbach and other researchers have found is that lower class sizes in grades K-3 significantly increase student achievement, both during grades K-3 and subsequent grades. In addition, lower class size in grades K-3 seems to have long-term effects in increasing the percentage of students who take college entrance exams such as the SAT or ACT, which suggests that more students who were in lower class sizes end up being interested in going to college and attending college.

Schanzenbach and other researchers have used these findings to estimate how the costs of lowering class size compare with the benefits of lower class size. Benefits are measured as the predicted increase in earnings for students due to lower class sizes, which can be predicted based on studies that predict students’ future earnings based on their test scores during school. The finding is that spending more money on lower class size has an estimated “real rate of return” (after adjusting for inflation) of 5 to 10 percent, which compares very favorably to most investments.

In sum, there is significant research evidence that devoting more resources to the classroom can pay off in increased student achievement. This increased student achievement then pays off in higher earnings and an expanded economy.