This study investigated whole class interactions in 200 science lessons involving 15 teachers and students from grades 8 to 12 in two urban Australian high schools. A relatively small number of 3-7 "target students" monopolized whole class interactions. In most instances target students were male. Compared to others in the class, target students asked more questions of the teacher, were called on to respond to higher cognitive level questions, and received higher quality feedback. Two types of target student were identified. The students who actively participated in classroom interactions in a self-initiated manner tended to accept responsibility for their academic achievement and for interactions with others. The second type of target student, who participated as a consequence of being selected by the teacher, tended to have higher formal reasoning ability and achieve at a higher level than others in the class. (Contains 2 tables and 1 figure.)