Cultural competency training programmes have been implemented in various educational settings to address diversity and inclusivity, but their impact on teachers' approaches remains understudied in Nigerian secondary schools. Ethnographic research was conducted by observing and interviewing teachers, students, and administrators in four randomly selected secondary schools across Nigeria. Data collection included classroom observations, semi-structured interviews, and document analysis. Teachers demonstrated increased awareness of cultural diversity but varied implementation strategies based on their initial levels of cultural competency, with some adopting more inclusive teaching methods while others maintained traditional approaches. This study highlights the need for ongoing professional development in cultural competency to enhance teachers' ability to effectively address diversity in the classroom. Schools should integrate regular cultural competency training into teacher induction programmes and provide resources such as curriculum materials that promote inclusive teaching practices. Cultural Competency, Nigerian Secondary Schools, Diversity Education, Teacher Training