This study examined the effect of the "Language Essentials for Teachers of Reading and Spelling" ("LETRS)" professional development curriculum on the reading achievement of second graders. The authors examined data on more than 5,000 second graders from ninety elementary schools in four states during the 2005-06 school year. Study schools were randomly assigned to one of three groups: one in which teachers received training following the "LETRS" curriculum, another where they received the "LETRS" training as well as ongoing instructional coaching, and a third where the teachers received the standard professional development available in their district. Thirty schools were assigned to each research group. The study measured effects by comparing the standardized reading test scores of students from each of the three groups of schools. Study authors reported that providing second-grade teachers reading instruction training using the "LETRS" curriculum (with or without the instructional coaches) did not increase the reading test scores of their students. What Works Clearinghouse (WWC) found the described research to be a well-implemented randomized controlled trial, consistent with WWC evidence standards. [The following report was the focus of this "Quick Review": "The Impact of Two Professional Development Interventions on Early Reading Instruction and Achievement" (NCEE 2008-4030). Michael S. Garet, Stephanie Cronen, Marian Eaton, Anja Kurki, Meredith Ludwig, Wehmah Jones, Kazuaki Uekawa, Audrey Falk, Howard Bloom, Fred Doolittle, Pei Zhu, and Laura Sztejnberg. Washington, DC: National Center for Education Evaluation and Regional Assistance, Institute of Education Sciences, U.S. Department of Education, September 2008 (ED502700).]