The subjects studied in the senior secondary years have a major influence upon subsequent educational and career options, and the choice of subjects has been seen as involving issues about equity between various social groups. Concern over equity in subject choice is expressed in relation to science because it is regarded as the basis for entry to many programs of professional education. It is argued that the much lower levels of participation by young women in physical science courses at school means that a range of vocational choices is subsequently denied to them. In a number of Western countries single- sex secondary schools or single-sex classrooms in coeducational schools are proposed as a means of improving the participation of young women in science courses. This chapter explores the influence of single-sex secondary schools, as well as other factors, on participation by young Australians in science in the final years of high school. [Introduction']