Two studies combining teacher questionnaires, classroom observation, and pupil interviews were conducted to contrast formal and informal teaching practices in open plan and conventional classrooms. Study I sampled 12 teachers of classes including second year junior pupils (8-9 years of age); Study II sampled 30 teachers, including 13 with mixed teaching styles. Instruments were chosen (or designed and piloted) to look at grouping patterns and organization within the classroom; organization and evaluation of the curriculum; patterns of movement and language in the classroom; and teaching styles and practices. Results indicated that formal teachers used class teaching significantly more than informal teachers; that there was a significantly greater proportion of teacher talk in the formal class; and that movement at pupils' discretion was not permitted except for queuing for teacher attention. No framework for pupil choice was provided. Small groups were used occasionally as an organizational device, but did not include pupil planning. Informal teachers structured a network of activities, providing significantly more simultaneously occurring activities and opportunities for pupil choice, including small group work involving pupil planning. There was significantly more movement at the pupils' discretion. Pupil talk was more valued than in traditional classrooms; more than 80 percent of the language to which the pupil was expected to attend was from peers. Appendices include the instruments used in the studies. (Author/SB)