The purpose of this research was to investigate the impact of teachers ‘personal development on pupils’ language performance, using CEG 2 GODOMEY as a case study. Teachers' personal development includes activities such as attending workshops, learning new teaching technics (direct instruction, indirect instruction, collaborative learning, active learning, learning through play, feedback, and reflection, etc.) and improving their skills. To achieve this, our goal, in-depth interviews, direct observation, and questionnaires were used to gather information. Informants were approached using purposive selection and simple random sampling. The results show that when teachers engage in selfdevelopment, their teaching improves, leading to better results in English for pupils. Teachers who take part in training and learning activities use more effective teaching methods, which translates into better results for pupils. Overall, the study shows that investing in teachers ‘personal development can lead to significant improvements in pupils’ language performance. The results suggest that schools should support in-service teacher training to improve students' educational outcomes.