Self-Contained ESL Classrooms: This approach is often used by districts and schools with large influxes of immigrants every year and with many beginning ELLs. Students first do academic work in their core subjects with other ESL students. Afterward, they are mainstreamed for non-academic subjects and noninstructional parts of the day, such as physical education, art, assemblies, study hall, library, computer lab, lunch, and recess. Classes usually contain students at mixed levels of English proficiency, meaning that the instructor must level instruction and plan small-group and whole-group lessons accordingly.