Field Experiments in Class Size from the Early Twentieth Century
梳理了二战前关于班级规模的现场实验，发现这些实验大多未证明小班教学能提高学生成绩，与部分现代研究结论相左，对教育政策制定者和研究者有参考价值。
A vast majority of adults believe that class size reductions are a good way to improve the quality of public schools. Reviews of the research literature, on the other hand, have provided mixed messages on the degree to which class size matters for student achievement. Here I will discuss a substantial, but overlooked, body of experimental work on class size that developed prior to World War II. These field experiments did not have the benefit of modern econometrics, and only a few were done on a reasonably large scale. However, they often used careful empirical designs, and the collective magnitude of this body of work is considerable. Moreover, this research produced little evidence to suggest that students learn more in smaller classes, which stands in contrast to some, though not all, of the most recent work by economists. In this essay, I provide an overview of the scope and breadth of the field experiments in class size conducted prior to World War II, the motivations behind them, and how their experimental designs were crafted to deal with perceived sources of bias. I discuss how one might interpret the findings of these early experimental results alongside more recent research.