The Kenyan government has been spending between 20% to 40% of its revenue on education with the aim to improving access and quality. Much of these resources have been devoted towards establishment and procurement of school inputs such as classrooms, teachers and textbooks. This study investigated the effects of funding on performance in Mumias District. Statistical proportionate and purposive sampling was used in identification of the sample. Piloting was conducted in two schools within the district. The study is based on the production function model which looks at the input--output relationship. Survey Questionnaires and interviews were used for data collection. Data were analyzed using descriptive and inferential statistics. The study established that there was a significant correlation between students' performance in Kenya Certificate of Secondary Education (K.C.S.E.) and school level of funding. Schools funded below 30% performed poorly in K.C.S.E. The study recommended that for performance to improve, day secondary schools which were the majority in the study need to be supported with learning resources. The findings of this study may be used by the stakeholders to improve on the quality of secondary education.