This paper presents three research studies. The first study investigated the use of boys' and girls' play areas, each stocked with sex-type toys, by day care children with male, female, or mixed teacher teams. Examined were the sex of play areas users and the effect of sex of teacher team on the structure of play in each play area. The second study considered the effects of men and women teacher teams on day care children's performance on tests of cognitive skill, cognitive style, and conservation of gender identity. Measurement involved the use of subtests from conventional intelligence tests, the Boy-Girl Identity Task, and tests of impulsivity-reflectivity. The third study sought to evaluate sex-typed classification of school objects by children in classes with teachers differing in sex. The study attempted to ascertain whether sex-typed attitudes were present at entry into the classroom and whether a year's exposure to men or women teachers affected their classification. Subjects for all three studies were 59 4-year-old preschool children attending a day care center in a working class community and nine teachers (five females and four males). The findings of each research project are discussed and illustrated with data tables. (SDH)