Across the United States, and in the states served by the Regional Educational Laboratory West (REL West) in particular, there is widespread concern about how to successfully educate the growing number of English language learner (ELL) students, especially those identified as long-term ELL students and those identified as reclassified fluent English proficient (RFEP) students who struggle to score at passing levels on state English language arts (ELA)/reading content tests. This study, which focuses on ELL students in Arizona, is one of a series of three companion studies that seek to help Arizona, Nevada, and Utah identify the characteristics of long-term ELL students and Struggling RFEP students. For this study, the authors defined "long-term ELL students" as students who, during the six school years of the study, never scored at or above the levels required on Arizona's English language proficiency (ELP) test to be reclassified as fluent English proficient. They compared these long-term ELL students to their ELL peers who did score at or above the levels required on Arizona's ELP test to be reclassified as fluent English proficient, whom we refer to as "reclassified fluent English proficient (RFEP) students." "Struggling RFEP students" were defined as ELL students who met the state's ELP requirements for RFEP but did not pass the state ELA or reading content test by the end of year 6 of the study. We compared these Struggling RFEP students to their RFEP peers who did pass the state ELA or reading content test, whom we refer to as "Transitioned RFEP students." The study examined student data from 2006/07--2011/12 to address three research questions: (1) What proportion of ELL students fit the study's definition of long-term ELL students by the end of the six years? What proportion of ELL students fit the study's definition of Struggling RFEP students by the end of the six years? (2) What are the characteristics of long-term ELL students? How are these characteristics different from those of RFEP students? (3) What are the characteristics of Struggling RFEP students? How are these characteristics different from those of the RFEP students who passed their ELA content test at least once by the end of the six years? The study followed three cohorts of ELL students in Arizona: a grade K cohort, who started kindergarten in 2006/07; a grade 3 cohort, who started grade 3 in 2006/07; and a grade 6 cohort, who started grade 6 in 2006/07. [This report, and the research on which it is based, were produced on behalf of REL West's English Learner Alliance, whose membership consists of the Arizona State Department of Education, the Nevada State Department of Education, the Utah State Office of Education, and the West Comprehensive Center. For the companion reports, see ED585540 (Utah) and ED585536 (Nevada).]