Well over a million students who are unfamiliar with the English language attend California’s schools, constituting about one-quarter of the state’s K-12 population. Given that proficiency in English is vital to success not only in academic subjects but also in the workforce, both state and federal policymakers consider English proficiency a major goal for English learner (EL) students. The federal government’s No Child Left Behind (NCLB) Act of 2001 establishes mandates for improving both the number of students achieving gains in English proficiency and the number who are reclassified as Fluent English Proficient (FEP). This report investigates how effective California schools are in achieving both NCLB goals. The authors examine the determinants of school-level reclassification rates (i.e., the school characteristics that seem to affect the percentage of EL students who are reclassified as FEP), and they also explore the student-level characteristics that appear to affect gains in achievement on an English proficiency test. The study identifies several categories of students who lag behind others in gaining English proficiency, and these distinctions should help policymakers target EL students who are in need of special assistance.