After discussing ways in which the concept of vulnerability is applied to children in psychology and sociology. It is argued that many of these may arise from the mistaken concretisation of essentialising concepts which have sometimes thereby become barriers to, rather than facilitators of, sociological understanding. Fieldwork is presented and analysed concerning the interactions of some London children, and their characterisations of themselves and others, in a variety of home, school and other settings. It is suggested that situations in which children are present often do generate ‘vulnerability’ in all participants not only in the children. In classrooms and elsewhere the attribution and reality of vulnerability moves rapidly between persons as situations develop and change.