Causality, causality, causality

"Educators and policy makers are increasingly intent on using scientifically-based evidence when making decisions about education policy. Thus, education research today must necessarily be focused on identifying the causal relationships between education inputs and student outcomes. In this paper we discuss methodologies for estimating the causal effect of resources on education outcomes; we also review what we believe to be the best evidence from economics on a few important inputs: spending, class size, teacher quality, the length of the school year, and technology. We conclude that while the number of papers using credible identification strategies is thin, the body of credible research on causal relationships is growing, and we have started to gather evidence that some school inputs matter while others do not."--Federal Reserve Bank of Chicago web site.