It has been argued that the establishment of single-sex classes for females can increase their motivation and participation in physics. This paper reports on findings from a multi-occasional study among 90 female year 11 physics students across single-sex and co-educational high schools in Australia. The aim of this study was to identify the differences in motivation, engagement and sustained enrolment plans in relation to physics between female students in single-sex from those in co-educational settings. Fine-grained analyses at a physics topic-specific level indicated differences between these cohorts in their interest value, career value, gender-stereotyped attitudes, performance perceptions, sustained engagement and sustained enrolment intentions in relation with physics. Results revealed that both cohorts have high levels of achievement motivation in relation to physics irrespective of their classroom composition; however, females from single-sex schools showed higher values for some constructs across various physics topics. This paper highlights the scarcity of research into females' sustained participation in physics, once they commence studying physics, and the difference class composition makes to females' achievement motivation and future enrolment intentions.