One quality indicator of intervention research is the extent to which the intervention has a high degree of social validity, or practicality. In this study, I drew on Wolf's framework for social validity and used qualitative methods to ascertain five middle schoolteachers' perceptions of the social validity of System 44®--a phonics-based reading intervention for secondary students. Findings derived from teacher interviews and classroom observations conducted during the course of one school year indicate that the ways in which teachers make decisions about social validity are complex and predicated on the interaction of several factors related to an intervention's goals, outcomes, and procedures. By using qualitative methods and applying Wolf's framework to an academic intervention, I expand the social validity construct and delineate its sub-components.