This study investigated the effect of group learning strategy with classroom activities on the academic performance of Basic 8 students in Basic Science in Makurdi Metropolis, Benue State. The study adopted a quasi-experimental pretest–posttest design without random assignment. A sample of 150 Basic 8 students were selected from a population of approximately 20,000 students in 30 secondary schools using multistage sampling. The participants were assigned to three groups of 50 students each: Group Learning Strategy (GLS), Group Learning Strategy with Classroom Activities (GLS+CA), and conventional lecture method. Data was collected using the Basic Science Performance Test (BSPT), which had a reliability coefficient of 0.82 using KR-21. Mean and standard deviation were used to answer the research questions, while Analysis of Covariance (ANCOVA) was used to test the hypotheses at the 0.05 significance level. Results showed that GLS recorded a mean gain of 8.46, GLS+CA 8.40, and lecture method 7.12. ANCOVA revealed a significant difference among the instructional strategies, F(2,146) = 9.649, p < .001, η²p = .117. Gender had no significant influence on performance under GLS, F(1,47) = 3.710, p = .060. The study concluded that group learning strategies are more effective than conventional instruction and are gender-inclusive. It recommends their adoption in Basic Science teaching. Keywords: Basic Science, Group Learning Strategy, Classroom Activities, Academic Performance, Gender, Junior Secondary Education, Nigeria