This study examines the implementation and organization of the state mandated curriculum in the 4-hour SEI block in 18 K-12 classrooms in 5 different districts. We focus on the effects of grouping by language proficiency, the delivery of the structure-based ESL curriculum, the provision of resources and limiting of access to grade-level curriculum, and problems of promotion and graduation for ELLs. In each of these areas, the implementation of the SEI 4- hour block raises concerns with regard to equal educational opportunity and access to English. Key among the findings of this study are: ELLs are physically, socially, and educationally isolated from their non-ELL peers; they are not exiting the program in one year, raising serious questions about the time these students must remain in these segregated settings; reclassification rates are a poor indicator of success in mainstream classrooms; and the four-hour model places ELLs at a severe disadvantage for high school graduation. The only means for these students to graduate with their peers appears to be through after school and summer school programs that either did not exist or had been cut. Appendices include: (1) Initial Visit Questionnaire for the Semi-Structured Interviews; (2) Materials and Resources; and (3) Parent Notification Form (ELLAR). (Contains 12 footnotes and 1 figure.)