The purpose of this study was to establish the extent to which school inputs affect the quality of education in day secondary schools in Kisumu County Kenya. The study was conducted in 18 day secondary schools, 18 head teachers, 123 teachers and 600 students. Proportionate sampling was used to select the number of day secondary schools in various divisions within the County. Simple random sampling was used to select the teachers and students for the study. Data was analysed using Linear multiple correlation. The most important inputs that affected the performance of the day secondary schools included involvement of Parents Teachers Association (PTA) in running of the schools; amount of instructional materials supplied and expenditure in laboratory equipment. The study recommended that PTAs should be strengthened, so that they could contribute to the provision of physical facilities in order to improve quality of education in the day secondary schools.