Slums areas present major social and health disadvantages to children, which may affect their school performance.The aim of this study was to determine the factors affecting scholastic achievement among adolescent children in a slum area. This cross-sectional study was carried out in an urban slum area (Manshiat Naser) in Cairo on a multistage stratified cluster sample of 200 preparatory school children residing in the area technique was used. The data collection tool was an interview questionnaire form covering socio-demographic characteristics, school achievement, and selected domains of the Global Risk Assessment Device (GRAD) scale. The fieldwork was from the beginning of October to the end of December 2015. The results showed that 18% of children had academic failure. Statistically significant relations were revealed between school achievement and school children's gender (p=0.001), age (p=0.03), grade (p=0.001), father education (p=0.02), mother age (p=0.19), residence (p=0.01), and income (p < 0.001). School achievement was also related to the educational (p < 0.001), accountability (p < 0.001), and health care (p < 0.001) factors of GRAD. In multivariate analysis, the risk factors predicting academic failure were a higher school grade, and higher scores of educational, accountability, and health care factors. In conclusion, the school performance of school children in slum area is most influenced by accountability, educational and health care factors, and higher school grade. Intervention studies are needed to investigate the effectiveness of school-based programs addressing these identified factors in improving school performance among these adolescents.