The paper examines the link between school effectiveness and academic performance among primary schools in Nairobi city, Kenya. Data are from 1120 teachers spread in 89 primary schools. Using multivariate regression analysis, the school effectiveness correlates and school academic performance are investigated. Results show existence of a latent variable that strongly explains academic performance even after accounting for covariates. This implies that poor parents in urban poor neighbourhoods choose to enrol their children in schools perceived to be effective; and, investment on strategies that enhance school effectiveness could go a long way to improve school academic performance.