In their analysis of National Assessment results Haertel et a1.t found that 13 year-old boys and girls are quite similar in science learning. However, this similarity does not exist for 17 year olds. One possible cause for this change is socio-cultural pressures. In this study, we suggest that the science classroom learning environment may contribute to these pressures due to differences in classes taught by male and female science teachers. The Learning Environment Inventory was used to assess student perceptions in junior high, biology, chemistry, and physics classes and significant differences were found. Students perceived classes taught by females as more formal, more goal directed, more diverse and as having more instances of teacher favoritism and friction between students. Classes taught by males were perceived as more difficult. Possible relationships between these perceptual differences and changes in girls' preference for science are discussed and suggestions for future research are given. Haertel et al. (1981), in their analysis of the 1978 National Assessment results for 13 years olds, report no sex differences in science achievement. They point out that these results are in marked "contrast to the highly significant differences between the sexes in science related attittudes, behaviors and aspirations during the late adolescence.'' Why does this change take place? It has been suggested that the development of cognitive differences among the sexes is related to cultural pressure (Fox, 1977). Bern, Pfeiffer, and Newman (1981) recently have documented an example of a cultural sexual bias. They found that both male and female teachers classified high achieving students as androgynous and masculine, while low achieving students were classified as feminine. Perhaps the change in girls' and boys' science learning is also related to socio-cultural factors, Haertel et al. state that learning has been shown to be positively related to nine factors: student age, ability, and motivation; the quality and quantity of instruction; the social-psychological environment or morale of the class and home; the peer group environment; and exposure