The research design involves the observation of a series of lessons. In the observation, three categories of classroom interaction are considered: instructing; questioning ; and cognitive structuring. The findings of the research show that the teachers do not adequately take the prior knowledge of pupils into account in the interactions which occur and in the tasks which are assigned to the pupils during lessons. When questions are asked, the correct answer appears to be more important than the pupils’ difficulties of understanding the content of the lesson. The teachers’ interactions with the pupils involve exchanges which do not resolve misunderstandings. The teachers do appear to have a tacit understanding of the importance of the prior knowledge of the pupils. The designs of the lessons are around a number of focal points. This seems to indicate that experienced teachers are able to maintain the flow of a lesson without planning the details of the whole lesson. The nature of the aims of the study precludes the development of and intervention strategies to improve the approach of the teachers.