Adolescent ELLs differ from native English-speaking students in the dual challenge they face: They must learn to speak, read, and write in English and master complex academic content at the same time. Aside from this common characteristic, however, adolescent ELLs come to the classroom with widely diverse education backgrounds and socioeconomic circumstances. Some are recent immigrants who received effective schooling in their countries of origin, are literate in their native language, and have excellent content knowledge even though they lack English skills. Others came to the United States as refugees fleeing violence, have attended school only intermittently or not at all, and lack basic literacy skills. Some are undocumented, which can affect both their socioeconomic status and, in some states, their postsecondary education opportunities. The largest group of adolescent ELLs (57 percent) were born in the United States but have not developed academic literacy in English for various reasons, such as high mobility.