This report synthesizes knowledge and instructional practices appropriate for effective instruction in classrooms comprised of students from three or more linguistic backgrounds. It specifically targets beginning teachers in Arizona, California, and Nevada schools where numbers of ethnically, culturally, and linguistically diverse students have increased dramatically. Following an introduction, the publication is organized into four sections: (1) "The Striking Contrast between the Region's Teachers and Students" presents facts and figures concerning changing student demographics and the concurrent lack of a demographic shift in the teaching force; (2) "Basic Knowledge about Language Development and Second Language Acquisition for Beginning Teachers" presents major findings from research on language development and second language learning, discusses the role of the students' first language in English acquisition, and draws implications of this research for beginning teachers who have not received special training to teach language minority students; (3) "Effective Instructional Practices With Language Minority Students" addresses English-language-development practices and ways to examine students' different cultures; and (4) "Training and Supporting Beginning Teachers in Diverse Settings' focuses on helping beginning teachers acquire knowledge and employ practices identified as effective in teaching language minority students. A 55-item reference list is appended. (LL)