This article examines cognitive models of peer learning in school and the implications that these models have for the teaching of science in primary schools. The article is a product of the European Commission, Socrates Comenius 2.1 funded project "The Implementation of Scientific Thinking in (Pre) Primary Schools Settings (STIPPS)" project (www.stipps.info). It reviews literature and examines the models developed to exemplify Piagetian and Vygotskian cognitive models of peer learning. The role that metacognition and affective development play in the peer learning process is explored. Research regarding the implementation of peer learning in school contexts is reviewed and recommendations are made as to a critical typology for the organisation and structure of peer learning in primary school science are made. The article provides a link between cognitive models of peer learning in primary school science and the classroom implementation of such models. The implications for continuing professional development of teachers in respect of the use of peer learning in science are explored and recommendations in this respect are made. (Contains 1 table and 2 figures.)