This report presents results from a new quantitative synthesis of research on the effectiveness and validity of test accommodations for English language learners (ELLs) taking large-scale assessments. In 2006, the Center on Instruction published a review of the literature on test accommodations for ELLs titled "Practical Guidelines for the Education of English Language Learners: Research-based Recommendations for the Use of Accommodations in Large-Scale Assessments" (Francis, Rivera, Lesaux, Kieffer, & Rivera, 2006). This new publication provides an update to the 2006 report, incorporating evidence from nine studies not previously included and providing updated recommendations for educators and policy-makers. Results drawn from 20 studies (including, in total, more than 33,000 students, of whom more than 9,400 were ELLs) were aggregated using meta-analysis. The studies were primarily conducted using researcher-created tests of mathematics and science with items drawn from the National Assessment of Educational Progress (NAEP) in grades 4 and 8. Drawing on the existing evidence, the authors suggest the following recommendations, ordered by the strength of the available evidence: (1) Use simplified English in test design, eliminating irrelevant language demands for all students; (2) Provide English dictionaries/glossaries to ELLs; (3) Match the language of tests and accommodations to the language of instruction; and (4) Provide extended time to ELLs or use untimed tests for all students. Appended are: (1) Characteristics of studies included in the meta-analysis on effectiveness of accommodations; (2) Comparisons of included studies to those included in Francis et al. (2006) and Pennock-Roman (2011) with reasons for inclusion for newly added studies since Francis et al. (2006); (3) Discussion of the choice of unit of analysis; and (4) Reporting of technical results. (Contains 3 tables and 3 footnotes.) [For related reports, see "Research-Based Recommendations for Instruction and Academic Interventions. Practical Guidelines for the Education of English Language Learners. Book 1 of 3" (ED517790); "Research-Based Recommendations for Serving Adolescent Newcomers. Practical Guidelines for the Education of English Language Learners. Book 2 of 3" (ED517791); and "Research-Based Recommendations for the Use of Accommodations in Large-Scale Assessments. Practical Guidelines for the Education of English Language Learners. Book 3 of 3" (ED517792).]