While some educators have attributed early school failure to improper grade placement and thus advocate grade placement according to developmental age, others believe that early school failure is due to the lack of academic preparation for young children by their parents or by preschools. This paper examines related literature for empirical evidence to support the developmental view of early school failure, exploring the history of developmental education as applied to school readiness and the use and effectiveness of developmental screening. The paper argues that research on developmental placement is not completely credible for three reasons. First, ambiguity in the definition of readiness used by researchers and educators reveals two different constructs of readiness: learning readiness, accepted by child development theorists, and school readiness, more focused on academic skills. Second, school districts with developmental transition programs in place fail to conduct meaningful longitudinal studies. Third, the validity of assessment tools for developmental age has been questioned. The paper concludes by asserting that more consistent and meaningful research is needed in connection with developmental placement and school readiness. (Contains 18 references.) (KB)