Comparative Effectiveness of Inquiry-Based and Conventional Methods in Developing Environmental Science Competencies Among Secondary Students in Delta State

This study compared the effectiveness of inquiry-based and conventional instructional methods in developing environmental science competencies among senior secondary students in Delta State, Nigeria. The Niger Delta region's unique ecological challenges make environmental science competency a particularly high-stakes educational outcome, yet empirical data on optimal instructional approaches for this outcome in the region are lacking. A quasi-experimental pretest-posttest design with two treatment conditions was used. Six schools in Warri South, Oshimili South, and Ughelli South Local Government Areas were randomly assigned to inquiry-based instruction, conventional instruction, or a combined approach. An Environmental Science Competency Assessment Tool was developed, validated by environmental educators, and confirmed reliable at 0.84. Analysis of Covariance and Bonferroni post-hoc testing were applied. Results showed that the inquiry-based group significantly outperformed the conventional group on both knowledge and applied competency subscales. The combined approach showed intermediate outcomes. Girls and students from lower socioeconomic backgrounds demonstrated disproportionately higher competency gains under inquiry conditions. The study fills a critical empirical gap in the regional science education literature and recommends a policy shift toward structured inquiry in the Environmental Science curriculum, supported by teacher capacity building and relevant contextual learning materials. Keywords: inquiry-based learning, environmental science, competency development, Delta State, secondary students.