Background: Early research exploring teacher expectations concentrated on the dyadic classroom interactions of teachers with individual students. More recent studies have shown whole class factors to have more significance in portraying teachers' expectations. Recently teachers having high or low expectations for all their students have been identified. Aims: The aim of the current investigation was to explore whether the classroom exchanges of high- and low-expectation teachers differed substantially and might be considered a mechanism for teachers' expectations. Sample: The participants were 12 primary school teachers from eight schools who had been identified as having expectations for their students' learning that were either significantly above or below the children's achievement level. The teachers formed three groups called high-expectation, low-expectation and average-progress teachers. Method: The participants were observed twice in the academic year during half-hour reading lessons. Two people observed each lesson, one completing a structured observation protocol and the other a running record and audiotape. Results: In contrast to the average progress and low expectation teachers, the high-expectation teachers spent more time providing a framework for students' learning, provided their students with more feedback, questioned their students using more higher-order questions, and managed their students' behaviour more positively. Conclusions: There appear to be important differences in the classroom environments for the students of high-expectation, average-progress and low-expectation teachers. The differences apply to both the instructional and socioemotional environments of the classroom. Such disparities may act as mechanisms for teacher expectation effects.