ABSTRACT The main objective of this ~tudy was to investigate the relationship between students poor performance in Mathematics and Sciences in K.C.S.E. examination and selected factors among selected schools in Embakasi Division of Nairobi District. The interest for the schools was strongly prompted by poor performance in these schools. The study used a survey method with application of Ex-post facto research design on 3 out of 20 schools in Embakasi Division. From these schools in 3 headteachers, 12 teachers and 60 students sampled from form 1-4. Two types of research tools which were used in the study to elicit data were questionnaires and interview. The obtained data was then used to determine whether relationship existed between the students poor performance in the K.C.S.E. and methods used. Based on the analysis, the students' performance correlated significantly with: Academic qualifications of teachers, Adequacy of teaching and resources in selected schools and attitude of students towards subjects. In brief the significant relationship reveals that listed factors had important impact on the poor performance of students in St. Mary High School, Embakasi Girls High School and Kayole Secondary in Embakasi Division. Consequently, the implication suggested by the findings of this study are that unless the recommended policies are implemented then the academic performance of students may continue to be poor.