Globally, stakeholders in learning institutions have strived to improve schools’ physical environments in an attempt to enhance learning outcomes. It is not known whether the physical environment in public secondary schools in Nairobi County have been mainstreamed to positively influence learning outcomes. The objective of the study was to explore the quality of the physical environment in public secondary schools in Nairobi City County, Kenya The study applied a case study design. A sample size of 39 was proportionally allocated by gender and geopolitical location resulting in 9 boys’, 12 girls’ and 18 mixed schools. A revised Commonwealth Association of Physical Environment questionnaire was used to collect data. The overall average quality of mixed schools’ index (126) was lower than that of boys’ and girls’ schools (134 for both). A framework of funding improvement of school facilities including the building stock and associated infrastructure is proposed.