Enabling pupils to become proficient at using spoken language is seen as one of the major goals of education. Pupils are expected to express their thoughts and engage with others in joint intellectual activity so as to advance their individual capacity for productive, rational and reflective thinking. The guided co-construction of knowledge, in which a teacher talks with pupils in whole class, group and individual situations to guide their thinking, together with opportunities for collaborative learning to promote critical thinking and problem solving, is, therefore, seen as being central to the educational process (Hardman, 2008a).