Physical sciences education comes with high expectations for learners to be successfully placed in tertiary institutions in related fields, and developing countries' aspirations to develop advanced and specialised skills to drive economies. However, some of the prevailing instructional strategies in science classrooms work to marginalise learners. This study explored access to effective inquiry-based practical work for physical sciences learners in two South African schools, through social cognitive and social justice lenses. Purposive sampling techniques were used to select an under-resourced high school and a well-resourced high school. Semi-structured interviews with two physical sciences teachers and open-ended observations were used to collect data in each of the schools for analysis through content analysis techniques. It came to light that the absence of practical examinations from the system of assessment resulted in an undervaluing of inquiry-based practical work in physical sciences classrooms. Additionally, instructional leadership practices did not support using this instructional strategy. The undervaluing of inquiry-based practical work marginalised learners, and the circumstances of limited access translated into a social justice agenda stemming from the high expectations associated with studying high school physical sciences. Recommendations are made to support inquiry-based practicals through the processes of assessment and tools for instructional leadership.