The study investigated the impact of computer simulations on the teaching and learning of photoelectric effect in Grade 12. The Grade 12 Physical Sciences curriculum has components of physics and chemistry. The photoelectric effect is a section in the physics curriculum and examination in the National Senior Certificate. In this case study, thirty learners were randomly divided into three groups in one rural school in the Frances Baard district in the Northern Cape Province. A randomised pre-test - post-test control group design was implemented. Data were collected through pre and post tests, by observation of the lessons and learner interviews. An analysis of variance performed showed that there was no significant difference on pre-test scores for the three groups. A paired -sample t-test on the post-test scores discovered that the Teacher-Centred Experimental Group (TCEG) performed better than the Learner-Centred Experimental Group (LCEG); (t statics, t (9) = -6.135, p < 0.05). In addition, the Control Group (CG) where the teacher used the traditional method of teaching performed even better than the Learner-Centred Experimental group. An analysis of covariance on the post-test scores with learners' pre-test scores as the covariate showed a significant effect on the instructional group favouring the TCEG (F (2,29) = 52.763, p < 0.05). The Hake's normalised gain, <g> was used to measure the effectiveness of the intervention. The normalised gain showed a high-g (0.794) for the TCEG, a medium-g (0.405) for the CG and a low-g (0.134) for the LCEG. The interview data also confirms that the TCEG learners benefited more than the LCEG learners. It is, therefore, suggested that the TCEG approach is a better method for the effective teaching of photoelectric effect. / Science and Technology Education / M. Sc. (MSTE)