This chapter addresses the question: How do classroom organizational and interaction patterns affect second-language learning? The concern here is not with formal instructional practices, but rather with informal strategies that teachers use in organizing the classroom: What kinds of groupings are optimal for secondlanguage acquisition? What kind of interaction patterns are set up by the teacher, consciously, and not so consciously? What interactions help children acquire the second language? What effects do teachers' attitudes and expectations have on second-language learning and school achievement?