The findings are presented of a study undertaken by the Southwest Educational Development Laboratory (SEDL) to assess the bilingual education services offered to limited English speaking students in three diverse communities and to study the extent to which the development of cognitive and academic skills in the native language and English are interrelated. The findings are integrated with current research and theory related to academic development in bilingual contexts, focusing on the policy implications of the SEDL findings. First, the general question of how research findings relate to educational policy is briefly considered. It is suggested that much of the confusion about the research basis for bilingual education derives from educators' and policy-makers' failure to appreciate the role of theory in the formulation of policy. The alternative policy-related theoretical arguments for and against bilingual education are outlined and the major SEDL study findings are examined in relation to these theoretical positions. The results of other related studies are reviewed and the extent to which policy-relevant theoretical principles emerge from the data is considered. (Author/MSE)