One hundred and sixty-five Year 7 (11-12 years old) pupils in co-educational schools in England participated in a study investigating the effects of mixed gender working on attitudinal and social measures. Eighty-two children working in mixed-gender groups and 83 control children working mainly in single-gender groups were tested on a variety of measures. Attitudes to science, social cohesion, self-reported individual learning, group learning, conflict resolution, and social facilitation, were recorded and analysed. In addition, pre-test and posttest evaluations were carried out and measures were related to test outcomes. The findings from the study indicated a positive effect of working in mixed groups: they were more likely than the control groups to like science lessons and consider taking it up as a subject in the future. Social measures indicated: (1) a better understanding of opposite-gender classmates, (2) a greater enjoyment of the collaborative nature of science, and (3) increased tendencies to offer academic support to peers. It is thus proposed that the integration of emotional learning within science lessons will facilitate boys' and girls' social development as well as increasing the likelihood of them being interested in science. These findings give support for the integration of emotional literacy with learning concepts in the science classroom and for co-educational schools.