Research indicates that boys perform better on mathematics tests while girls perform better on reading tests. An investigation of why boys' and girls' performance differs was made by coding teacher interactions with second grade students during reading and mathematics instruction. Results reveal that teachers: made relatively more academic contact with girls in reading and with boys in math; spent the same amount of time with boys and girls in both subjects; made more managerial contacts with boys in general; and, while there are no differences in initial abilities, sex differences were found in end-of-year achievement. (Author)