This study examines teacher-student interactions and selected student gender differences with volunteer boys and recruited girls in a technology class. The participants were teachers and triads of girls and boys in single-gender sections of a technology course where the students built, designed features for, and programmed Lego robots. We analyzed transcripts of videotapes of instruction; teacher, parent, and student interviews; student questionnaires; and final programs. Girls and boys differed in a number of ways, and teachers explained their differing interactions with boys and girls as functional responses to those differences. At the end of the course, volunteer boys and recruited girls did not differ in achievement or interest in the course. (Contains 5 tables.)