To gather information to assist policy makers, curriculum designers, and classroom teachers in planning and delivering language and reading instruction that will promote success in school of children from complex language backgrounds, a 6-year longitudinal investigation begun in 1978 tracked approximately 250 Spanish-speaking children from low income families taught by over 200 teachers in 20 schools in 5 Texas school districts from kindergarten through second or third grade. Oral language proficiency tests, teacher ratings, and audiotaped interactions were used to evaluate oral skills development while reading achievement was measured using Spanish and English versions of the Interactive Reading Assessment System and other standardized tests. Issues considered as a result of study findings included valid language assessment, language criteria for program placement, length of stay in bilingual programs, language development and reading acquisition, pre-reading skills development, rate/pattern of language/reading growth, transfer of skills across languages, precursor skills, nominal instructional programs, quantity and quality of instruction, practices associated with less student gains, and site characteristics. Based on correlation and regression results, predictor variables of kindergarten entry language skills, performance during the previous year, and the quantity and quality of reading instruction were most strongly related to reading achievement within each of the instructional years. A two-page list of references concludes the document. (NEC)