This paper looks at the amount of students' participation in instances of two common instructional arrangements, whole-class and small-group discussions, in a sixth-grade science class. The purpose is to understand how best to allow girls equitable access to the kinds of social interaction shown to be necessary for science learning. It is first established that although the teacher believes in making room for everyone to talk, girls talk significantly less than boys do in whole class discussions run by this teacher. It is further shown that small groups afford different participation structures than the one-at-a-time talk of the whole class, and that turns are often distributed more equitably in these small groups than in whole class discussion. For each arrangement the paper begins to identify some strategies students use to gain turns at talk. It suggests that the more control these students had in establishing the participation structures, the more equitable was the participation from various students. (Author)