Field Experiments in Class Size from the Early Twentieth Century

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 conclude with a discussion of how one might interpret the findings of these early experimental results alongside more recent research, and how research on class size has shifted towards using instrumental variables rather than field experiments to address the class size issue empirically.