Background/Context In September 2007, the Arizona State Board of Education adopted the Structured English Immersion (SEI) model proposed by the Arizona English Language Learner (ELL) Task Force.During the 2008-2009 academic year, it required all school districts to implement the SEI model.The SEI program, best known as the 4-hour English Language Development (ELD) block, was designed to accelerate the learning of the English language, and the goal set forth in Arizona law is for ELLs to become fluent or proficient in English in one year. The SEI model has been implemented in the state of Arizona for two academic years. Unfortunately, little empirical evidence exists regarding the effectiveness of this model, particularly from the perspective of teachers. Purpose/Objective/Research Question/Focus of Study The objective of the present study is to determine teachers’ perceptions of what is working most effectively to provide Arizona's English learners with a quality education. Of particular interest is to better understand: (1) Teachers’ knowledge, opinions, concerns, and understandings about the curriculum and pedagogy for ELL students, (2) How well prepared teachers feel they are to deliver the 4-hour ELD block curriculum, and (3) Teachers’ opinions of how well ELLs are advancing toward meeting the goal of English proficiency and the state educational standards that are set for all of Arizona's students. Population/Participants/Subjects The participants of this study include a sample of 880 teachers currently teaching in 33 schools across the state of Arizona. The sample of schools is representative of the state of Arizona in the distribution of ELL students across grades, but not in terms of students’ demographic characteristics. Furthermore, the sample of teachers in this study is representative of the state of Arizona in terms of gender and level of education, but not in terms of teachers’ ethnicity. Research Design A survey was designed around several areas of interest: (1) descriptive characteristics of teachers, (2) teachers’ perceptions of their current level of preparation for teaching ELL students in the 4-hour ELD block, (3) teachers’ perceptions of effectiveness of the 4-hour ELD block, (4) teachers’ perceptions regarding the academic potential of ELL students, and (5) teachers’ opinions about the implementation of the 4-hour ELD block. Several analytic tools were used to analyze the data collected, including descriptive statistics, t-tests, and Analysis of Variance [ANOVA]. Findings/Results Findings of this study are presented around 6 specific areas of interest: (1) teachers’ perceptions about their current level of preparation for teaching ELL students, (2) teachers’ beliefs about the academic potential of their ELL students (3) teachers’ language beliefs, (4) teachers’ perceptions of the effectiveness of the 4-hour ELD block, (5) teachers’ perceptions about the educational opportunities offered to ELL students, and (6) segregation of ELL students for purposes of instruction and teachers’ opinions about segregation of ELL students and its consequences. Conclusions/Recommendations Based on the findings of this study, we offer the following recommendations. First, Arizona should consider offering alternative modes of instruction that can help ELL students access the course content needed to succeed academically. And second, Arizona should find ways to offer ELL students support from their English proficient peers in acquiring and using language in the classroom, particularly with the complex academic language that leads to successful high school graduation and higher education opportunities.