This paper estimates the effect of school and student characteristics on academic performance. Using data for 2002, the paper applies stochastic frontier techniques to estimate the level of technical efficiency of a sample of 4,542 public and private schools. Our findings indicate that both school and student characteristics have a positive and significant effect on academic performance. It appears that private schools are more efficient due to a more favourable environment since, on average, they receive students from higher income families. However, assuming a similar environment, differences in efficiency levels between private and public schools tend to disappear.