This study explored Grade 10 learners’ science conceptual development when conducting practical work using Computer Simulations (CS) and compared achievements with those from Traditional-Chalk-and-Talk (TCT). A pre- and post-quasi-experimental research design was used. 53 learners were assigned to the Experimental Group (EG) and 52 to the Control Group (CG). The EG was taught using CS, while CG used TCT. Interviews were used to identify learners’ experiences after interventions. The overall results show that learners in EG enjoyed science and developed conceptual understanding better than those in the CG (T-test, p < 0.05), (ANCOVA, p < 0.01). The achievements of girls (M=54.60, SD=10.93) and boys (M=54.39, SD=7.90) in EG after intervention were not significantly different t (51) =-0.08, (p < 0.05). Despite the high learner-to-computer ratio environment, these results compare well with those of low learner-to-computer ratio and this is good news to developing countries where there are limited resources.