The focus of this study was the differential effects of a bilingual teacher and a nonbilingual teacher on the activity and interaction systems of classes where approximately 80 percent of the children were from bilingual homes. Special emphasis is on the general effects of teacher behavior on learning. Two teachers in an open-classroom school were observed for a year. A narrative of class activities was developed. The analysis of the data described (a) relations between levels of instruction, (b) inconsistencies in curricular packages, (c) visual transmission of teacher norms, (d) time-of-day variables related to teacher-student interaction, (e) ambiguous teacher-specialist relationships, and (f) observer influences on teacher activity and teacher-student interaction. (JS)