Purpose: The purpose of this study was to determine the degree of implementation and importance of the 7 domains of effective school practice for English language learners (ELLs) (Williams, Hakuta, & Haertel, 2007) as perceived by principals and teachers of elementary schools serving ELL populations of 40% or greater that met AYP goals and those that did not meet AYP goals for 2 consecutive years; in addition, the study intended to determine whether there were significant differences between the perceptions of these 2 groups. Methodology: A quantitative study, using descriptive and inferential statistics, examined principal and teacher ratings of effective and noneffective elementary schools using a 40-item survey. The survey instrument was developed by the researcher utilizing Williams et al.'s (2007) work and the California Professional Standards for Educational Leaders (CPSEL) (WestEd, 2004). Findings: Effective elementary schools (a) use assessment data to improve student achievement and instruction; (b) put into practice and believe that the implementation of a coherent, standards-based curriculum and instructional program is important in improving the academic achievement of English language learners; (c) put into practice and believe that prioritizing student achievement through the use of measurable and monitored objectives is important in improving the academic achievement of ELLs; and (d) identify at-risk students and respond with appropriate instructional interventions to a greater degree than noneffective schools. Conclusions: The findings revealed varying degrees of implementation and importance of the 7 domains of effective school practice as identified by effective and noneffective elementary schools. Effective schools identified specific domains and practices which were implemented and were considered important in improving the academic achievement of English language learners. In addition, effective schools implemented particular practices to a greater degree than noneffective schools. Recommendations for Further Research: Further research can be conducted on the 7 domains of effective school practices for English language learners as outlined by Williams et al. using a self-reporting instrument for principals and other stakeholder groups to gain an in-depth understanding of the leadership style, characteristics, or traits needed by principals to fully implement the 7 domains to further build the body of knowledge of effective schools. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]