In this study – the outcome of three years' participant observation in local authority primary and secondary schools – the classroom teacher is shown to have a far greater impact upon and responsibility for his pupils than is generally admitted. The teacher's perceptions of the children in his class are demonstrated to have a more important bearing on the pupils' attainment than the major factor of their social class. In carrying out this research, Roy Nash has moved outside the mainstream tradition of educational psychology to take into account the methods of anthropology and sociology. He shows, by looking at the actual behaviour of teachers and children in classrooms, and by following the pupils from several different primary schools through to the same local authority secondary school, how the teacher's expectations for his pupils can act as self-fulfilling prophecies. The author's illuminating research is illustrated with tables and with three Appendices.