As a part of a longitudinal study of learning in open plan and conventional design classrooms, the present study focuses on school design and its influence on selected behavior of pupils and teachers. The behaviors of pupils and their teachers in eleven learning areas of open plan and seven of conventional design were observed. Among the 18 classrooms, differences were found in the usage patterns of the major learning areas and in the nature and frequency of interaction between pupils and teachers. Compared with their peers in the conventional classrooms, pupils in the open plan classrooms were less often observed working by themselves but more often observed in small-group work and in communication with their peers and teachers. However, school design did not appear to be a critical factor that could explain most of these differences. It is proposed that school design is a less powerful determinant of teacher behavior than school organization and teacher tradition are. (Author/MLF)