In response to the recent publication and media coverage of several books that support educating boys and girls separately, more public schools in the United States are beginning to offer same-sex schooling options. Indeed, students may be more comfortable interacting solely with same-sex peers, as boys and girls often have difficulty in their interactions with each other; however, given that boys and girls often interact beyond the classroom, researchers must discover why boys and girls suffer difficult other-sex interactions and determine what can be done to improve them. We present two studies aimed at examining such processes. Both studies were conducted from a dynamical systems perspective that highlights the role of variability in dyadic social interactions to capture temporal changes in interpersonal coordination. The first focused on the utility of applying dynamics to the study of same- and mixed-sex interactions and examined the relation of the quality of those interactions to participants' perceptions of their interaction partners. The second study was an extension of the first, examining how dynamical dyadic coordination affected students' self-perceived abilities and beliefs in science, with the intention of examining social predictors of girls' and women's under-representation in science, technology, engineering, and mathematics.