• teacher education-practicing teachers;
  • diversity;
  • urban education;
  • elementary


This study examined the effect of fidelity of implementation (FOI) on the science achievement gains of third grade students broadly and students with limited literacy in English specifically. The study was conducted in the context of a professional development intervention with elementary school teachers to promote science achievement of ELL students in urban schools. As the criterion for measuring FOI, we focused on the quality of instructional delivery in teaching science to ELL students. We measured FOI using both teachers' self-reports and classroom observations during the first year of the intervention. Science achievement was measured by a pretest and posttest over the school year. The results indicate that none of the measures of FOI using teachers' self-reports or classroom observations had significant effects on science achievement gains. The results are discussed in terms of issues about conceptualization and measurement of FOI in educational interventions. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 46: 836–859, 2009