It is well-recognized that women are underrepresented in science and engineering studies. Their low representation is cause for concern because of its implications for the quality of the scientific and engineering labor force in the United States. It is well-known that gender differences in performance and interest in science and mathematics begin as early as junior high school. Understanding the factors that contribute to the differences are crucial in bringing about change. This research on antecedents of academic achievement will contribute to understanding this crucial period. The research focuses on home and school circumstances, including parental encouragement and peer pressures, that contribute to change in academic achievement over a two to four year period after 7th and 9th grades. The sample includes 2,236 students who attended 14 South Carolina public schools in 1986. The results will show how differential development in academic achievement of girls and boys during adolescence is related to a variety of conditions in early adolescence, reflecting the student's abilities and orientations, and his/her relationships with the major agencies of socialization--the family, the school, the peer group, and mass media.