In a previous Swedish twin project (the SLU-project), approximately 300 MZ and DZ twin pairs and controls were followed through the Swedish compulsory school from grade 3 to grade 9. Results from this study indicated an increase of genetic influences on school achievement over time for children from a permissive home environment and a decrease for children from a restrictive home environment. These types of data have generated a more general model for studying heredity-environment interaction in educational settings. To test this model, a cross-cultural comparison over time of twins and controls in the Israeli kibbutz school and in the Swedish compulsory school has been made. Restrictions on the child were originally assumed to be more apparent in the kibbutz environment.
