Education serves as a vital instrument for national development, social transformation, and human capital formation. Within the educational system, classroom management plays a significant role in shaping students’ academic achievement and overall learning outcomes. This study examined the influence of classroom management on students’ academic achievement in public secondary schools in the Federal Capital Territory (FCT), Abuja, Nigeria. Specifically, the study investigated the influence of classroom discipline and teacher–student relationship on students’ academic achievement. A descriptive survey research design was adopted for the study. The population comprised teachers and students in public secondary schools in FCT Abuja. A sample of 200 respondents was selected using a simple random sampling technique. Data were collected using a structured questionnaire titled Classroom Management and Students’ Academic Achievement Questionnaire (CMSAAQ). The instrument was validated by experts in Educational Management and Measurement and Evaluation, and a reliability coefficient of 0.81 was obtained using Cronbach Alpha method. Mean and standard deviation were used to answer research questions, while Pearson Product Moment Correlation was used to test the hypotheses at 0.05 level of significance. The findings revealed that classroom discipline and teacher–student relationship significantly influence students’ academic achievement in public secondary schools in FCT Abuja. The study concluded that effective classroom management enhances students’ academic performance by creating a conducive learning environment and promoting positive interactions between teachers and students. The study recommended that teachers should maintain effective classroom discipline, adopt modern classroom management strategies, and foster positive teacher–student relationships to improve academic achievement. Government and educational stakeholders should also provide supportive facilities and training opportunities for teachers to enhance classroom management practices.