Schools in Pakistan face many challenges, ranging from lack of qualified teachers to insufficient teaching resources. Another obstacle is the low quality of school built environment. Some important built environment factors include an available water supply, sanitation facility, electricity access, proper seating arrangement and space, and school age. The quality of most schools’ built environment in Pakistan is poor because schools are either built poorly or not well-maintained. Scholars have rarely studied the effects of school built environment on educational outcomes in Pakistan. Therefore, this study investigates the effects of school built environment on achievements of 72,843 students in grades 1 to 10. The study uses secondary data collected in 2015 by the Annual Status of Education Report (ASER) Center, a Pakistani nongovernment organization. The data come from a nationwide random sample of 5,296 Pakistani schools. Indicators of the built environment in multi-level regression models are the facility’s age and if school has electricity, water supply, toilet facilities, a boundary wall, multi-grade classrooms, and seating arrangement. The models control for student and family background characteristics, urban or rural school location and public or private sector affiliation. Findings indicate that variations in school built environment are significantly related to variations in academic achievement. The better the built environment, the higher the students’ achievement in all grades. The study also finds the impact of school built environment on academic achievement is conditioned by gender, such that female students are more vulnerable than male students to the effects of variations in school built environments, particularly due to the absence of sanitation and water. Findings highlight the importance of school built environment for student performance. Given the paucity of research on the issue, this study contributes to the existing literature on the topic. Policy implications of the findings are considered.