In this paper we present a comprehensive model of instruction for providing consistent, high quality teaching to L2 students. This model, the SIOP Model (Sheltered Instruction Observation Protocol), provides an explicit framework for organizing instructional practices to optimize the effectiveness of teaching second and foreign language learners. The SIOP Model includes features that promote acquisition of both subject area content (e.g., math, science, literature) and language development (the target language). The SIOP Model is presented in the context of three settings: immigrant students who may or may not have grade-level literacy in their mother tongue, bilingual students who are learning content through a foreign language and students of English as a foreign language who are learning professional content in English through English for Specific Purposes (ESP) course. Our experience from all three settings indicates that there is significant improvement in achieving the learning outcomes for English Language Learners by using this model of instruction.