Laboratory-Based Pedagogy (LBP) is widely advocated for promoting active, inquiry-based science learning. Yet, evidence of its effectiveness at the junior secondary school level remains underexplored in developing educational contexts. Guided by Piaget's constructivist theory, this pilot randomised pretest-posttest study examined the effect of LBP on Basic Science achievement among 30 junior secondary students from a single school, randomly assigned to experimental (n = 15) and control (n = 15) groups. The experimental group engaged in structured hands-on laboratory activities integrated into classroom instruction, whereas the control group received teacher-centred instruction covering the same content. Data was collected using the Basic Science Achievement Test (BSAT), adapted from National Examination Council (NECO) examination items. Mean scores, standard deviations, and Analysis of Covariance were employed to analyse the data, while controlling for pretest scores. Result revealed a significant effect of instructional method on posttest achievement, F(1, 27) = 19.44, p < .001, partial η2 = 0.419, with the laboratory-based group outperforming the control group. Pretest achievement also significantly predicted posttest performance. These findings suggest that LBP can improve Basic Science achievement by promoting active learning. Nevertheless, the findings should be interpreted with caution because the study was conducted at a single school, involved a small sample, and the groups exhibited substantial baseline differences in pretest performance. The study provides preliminary evidence to support larger, well-powered randomised trials in diverse educational settings.