In 2018, Sierra Leone introduced the Free Quality School Education (FQSE) programme to reduce the direct cost of schooling and improve access, equity and learning conditions. This study examined the relationship between FQSE, access to science education and pupils’ performance in core science subjects at the West African Senior School Certificate Examination (WASSCE) in Southern Sierra Leone from 2020 to 2025. A descriptive cross-sectional survey was combined with a retrospective analysis of aggregated examination records. The study involved 400 respondents from 20 government and government-assisted secondary schools in Bo, Bonthe, Moyamba and Pujehun districts: 320 pupils, 60 science teachers and 20 principals. Data were analysed using descriptive statistics and trend analysis. Findings showed substantial improvement in access. Among pupils, 89.7% reported that FQSE enabled more children to attend secondary school, while 86.9% said it reduced the financial burden on their families. Teachers also reported improved access (95.0%), but noted increased workload (90.0%) and larger class sizes (86.7%). Resource gaps remained evident, as only 53.4% of pupils and 45.0% of principals considered laboratory facilities adequate. Aggregated WASSCE core-science pass rates increased from 55.0% in 2020 to 67.0% in 2025. The findings suggest that FQSE is associated with improved access and participation, but science achievement continues to be constrained by inadequate laboratory resources, staffing, class size and learning materials. Continued investment in science teaching and learning is therefore necessary.