In this commentary, we complement other constructive critiques of educational randomized control trials (RCTs) by calling attention to the commonly ignored role of context in causal mechanisms undergirding educational phenomena. We argue that evidence for the central role of context in causal mechanisms challenges the assumption that RCT findings can be uncritically generalized across settings. Anchoring our argument with an example from our own multistudy RCT project, we argue that the scientific pursuit of causal explanation should involve the rich description of contextualized causal effects. We further call for incorporating the "evidence" of the integral role of context in causal mechanisms into the meaning of "evidence-based practice," with the implication that effective implementation of practice in a new setting must involve context-oriented, evidence-focused, design-based research that attends to the emergent, complex, and dynamic nature of educational contexts. [For the Grantee Submission, see ED605239.]