The goal of English as a second language (ESL) instruction in Massachusetts public schools is to advance English Learners’ (ELs) language development and promote their academic achievement. English language proficiency includes social and academic language in listening, speaking, reading, and writing (WIDA, 2012a). ESL instruction provides systematic, explicit, and sustained language instruction, and prepares students for general education by focusing on academic language while also attending to social instructional language. Effective ESL instruction supports student success in school, including improvement of ACCESS scores and acceleration of academic achievement. It also supports long-term goals such as college and career readiness. ESL instruction, with its own dedicated time and curriculum, is a required component of any program serving ELs in Massachusetts (Sheltered English Instruction, Two-Way Immersion, Transitional Bilingual Education). ESL instruction is not an intervention.