Acculturation and biculturalism of four populations (first-, second-, and third-generation Mexican American school children, and a comparison group of Anglo American children) were measured by teacher ratings of classroom behavior, using the Bicultural Identity/Respect for Cultural Differences Scale, developed expressly for use in bilingual/bicultural programs where instruction is in English and Spanish and children have opportunities to role-play characters of different cultural backgrounds. The 80 second and third graders (ages 7 to 9) were divided equally by sex and grade into each of the 4 groups. All subjects, enrolled in a semi-rural/suburban elementary school in Southern California, participated in the school's bilingual/bicultural Follow Through Program, with instruction in both English and Spanish. Results showed that of the three Mexican American groups, third-generation children were most similar to Anglo American children in their levels of acculturation with both Mexican American and Anglo American cultures. Although first-generation children were most strongly identified with Mexican American culture, they were also the most bicultural. Except for third-generation children, the trend was for all groups to be bicultural. Analysis showed no significant sex differences. Findings are discussed in terms of their implications for the development of a bicultural identity. (AW)