Family socio-economic status affects children's education. It has been noted that the girl child is performing poorly in Kisumu East District when compared to the boy child in Kenya Certificate of Secondary Education Examinations. For instance in 2008, in Nyanza Province only 5 girls compared to 25 boys were ranked among the top 100 nationally. Among the 5 girls there was only one girl from Kisumu East District. In 2009, only 6 girls compared to 26 boys were ranked among the top 100 position nationally from Nyanza Province; and there was no girl while there were 4 boys from Kisumu East District. Therefore the purpose of this study was to find out the influence of family socio-economic status on academic achievement of secondary school girls in Kisumu East District. The objectives of the study were to: examine the influence of parental level of Education; find out the influence of family income; establish the influence of family size and birth order and find out the influence of cultural factors on girl student academic achievement. The theory used was Pearson's gender relations theory (Pearson, 1995). The research designs used were correlation and descriptive survey designs. The s