The quality of the school environment remains an important determinant of effective teaching, learning, and students’ academic achievement. This study investigated the influence of school environment on students’ academic achievement in selected public secondary schools in Nigeria, with particular emphasis on school climate, teacher discipline, and physical facilities. The study adopted a descriptive survey research design. The study population comprised 1,636 teachers from 119 public secondary schools, from which a sample of 250 teachers was selected using simple random sampling. Data were collected using a researcher-developed 15-item structured questionnaire titled “Influence of School Environment Questionnaire (ISEQ).” The instrument was validated by experts in Educational Management and Tests and Measurement and yielded a Cronbach’s alpha reliability coefficient of 0.83. Mean and standard deviation were employed to answer the research questions, while Chi-square (χ²) statistics were used to test the hypotheses at the 0.05 level of significance. The findings showed that school climate was perceived to have a significant influence on students’ academic achievement. Teacher discipline was also significantly associated with academic achievement, indicating the importance of punctuality, regular attendance, professional conduct, effective lesson preparation, and adherence to school regulations in promoting students’ learning outcomes. Furthermore, the adequacy and quality of school physical facilities significantly influenced students’ academic achievement. The study concludes that improving students’ academic achievement requires sustained attention to both the physical and psychosocial conditions within public secondary schools. It recommends strengthening school infrastructure, promoting positive school climates, ensuring adequate provision and maintenance of instructional facilities, and enhancing teachers’ professional discipline.