This paper provides an introduction to a study of the ecological understandings of children aged 5‐16 years in schools in the north of England. Children's ideas about selected ecological concepts were elicited through a series of written tasks and individual interviews set in a range of contexts, referred to here as probes. Responses of about 200 pupils, across the age range, were obtained on each probe. In this paper, issues relating to theoretical background, design and methodology are outlined. Two further papers present the major findings of the study: the first reports children's ideas about the cycling of matter between organisms and between organisms and the abiotic environment (Leach et al. in press a); the second reports children's ideas about the interdependency of organisms in ecosystems (Leach et al. in press b).