This report presents results of research conducted in conjunction with a Swedish project focused on the bilingual instruction of immigrant children. The main aim of the project was to construct a model for teaching children with a mother-tongue other than Swedish (in this case, Finnish) in a way that would provide them the same educational and developmental opportunities as Swedish children. The report discusses the teaching model used by the project for the first three years of comprehensive schooling and the effects the model had on the progress of the children. The teaching model used in the project combined in one class a group of Finnish pupils and a group of Swedish pupils. The immigrant pupils were taught by both a teacher speaking their mother-tongue and a Swedish teacher who also instructed the Swedish-speaking pupils. Four cohorts of Finnish immigrant children born in successive years between 1966 and 1969 participated in the project and the research. Cohorts were formed by offering free places in a bilingual preschool program. The original number of children in each cohort was between 11 and 15. Data, collected continuously from 1972 to 1979 for the four cohorts, consisted of Finnish and Swedish school and language proficiency tests, teachers' observations and ratings, intelligence tests, and interviews with parents. The results of several different comparisons of populations and explorations of relationships between variables are reported. (Author/RH)