Summary.There is still much debate, particularly in North America, about whether teachers' expectations have an effect on pupils' achievement, and through which factors expectations might be mediated. This paper reports on associations between teachers' academic expectations at the beginning, and children's attainments at the end of the school year. The study took place in infant schools in London. Associations were significant during all three years of infant school, and were not explained by children's attainments at the time of the expectation rating. Range of effects, in standard deviation units, of associations between expectations and progress over the school year ranged from 0.4 to 0.8. Two possible mediating factors between expectations and attainment were explored: differential curriculum coverage and differential classroom behaviour. It was found that children for whom teachers had higher expectations were given a wider range of activities in written language and mathematics, and this was so over and above attainments at the beginning of the school year. In contrast, there was no evidence that expectations were related to measures of classroom interaction like teacher praise and instructional contact.