This paper draws upon data gathered from a research project entitled "Children's Relationship Cultures in Years 5 and 6". The project aimed to explore the ways in which primary school age children understand emotional, caring and family relationships. This paper will focus upon the ways in which gender and sexuality is performed by boys and girls in a UK primary school. An ethnographic approach is adopted to document the variety of social interactions within pupil cultures and the implications of these for sex-gender identities. Finally, the paper discusses how an understanding of the ways in which gender and sexuality feature within pupil cultures can inform curriculum issues and pedagogic practice. (Contains 4 notes.)