This booklet aims to help educators make informed decisions about which students need special language services, what kind of services they should receive, and how well the students and the language program have succeeded. It focuses on the following issues: (1) how the larger social context affects teachers' decisions and students' success; (2) the diversity of limited English proficient (LEP) students; (3) which instructional models and curriculum designs appear to be most effective, with an emphasis on transitional bilingual programs; (4) the necessity of integrating staff development and supervision for teachers of LEP students into the mainstream of the school; and (5) methodological difficulties in assessing student progress and evaluating program effectiveness. Conclusions and recommendations are included, as is a list of references. (PS)