Multilingual classrooms are becoming the norm in the global North due to the constant shifting of populations. Yet most of the instruction still tends to be in the major or official language of the country. Teachers find themselves in educational contexts that instruct in one language to multilingual populations with varying degrees of language proficiency. In this new world order, teachers need to be prepared to work with bi/multilingual students in ways that enhance students’ chances of succeeding in school by acquiring a new language, learning the content of various disciplines, and developing a healthy bi/multilingual and bi/multicultural identity. Teachers prepared to work with students from language backgrounds different from the school language make an effort to know their students, understand bilingualism and second language learning, and know the disciplines they teach and the language needed to express the content of the disciplines. These teachers are capable of creating quality curriculum, classroom environments, and instruction that supports learning, regardless of students’ proficiency in the language of instruction. The recommended knowledge-base and instructional approaches for these kinds of contexts are an opportunity to reform schools to be aligned to the reality of 21st-century schools.