Outlined are factors in effective instruction for linguistically diverse students in the public schools, particularly when those students are not enrolled in English-as-a-Second-Language or bilingual education programs but are integrated with English-proficient students in the regular classroom. The term "mainstreaming" is defined as it is applied to this population, and guiding principles for effective classroom mainstreaming are presented. Classroom instructional behaviors and techniques found to be effective in supporting the learning process of linguistically diverse students are specified, most concerning classroom communication and presentation of information. Classroom activities recommended for use with this population are listed, and common characteristics of urban children are noted. A series of useful strategies to be used individually or combined for effective instruction are detailed, and a checklist of questions the teacher can ask himself concerning the students, syllabus, instructional materials, and teaching techniques is included. Individual and classroom factors affecting second language acquisition are described, and considerations in assessment are examined. (MSE)