Co-educational (Coed) high schools, it is frequently argued, provide a more natural social environment to prepare adolescents to take their place in a society of men and women than do single-sex (SS) schools (e.g. Dale, 1969, 1971, 1974). Based in part on this contention, public single-sex schools are declining in numbers in most western societies. Coleman, however, challenged this contention and suggested that coeducation ‘may be inimical to both academic achievement and social adjustment’ (1961, p. 51). More recently, other researchers have proposed that co-education may be detrimental to the academic or social development of girls (see Bone, 1983; Jones et al. 1987; Mahony, 1985; Shaw, 1980; Spender & Sarah, 1980; Willis & Kenway, 1986). Willis and Kenway, for example, noted that ‘single-sex schooling, in some form, is offered by many feminists as one strategy for overcoming sexist educational practices’ (p. 132), but they noted the dubious logic and evidence typically used to support this strategy. Given the important policy implications of such questions, there is surprisingly little well-controlled research.