Using a sample of countries chosen for their similar level of development, this article shows the extent to which the organisation of primary and secondary education differs from one country to another, notably with respect to the way in which systems differentiate and select pupils for specialised curricula. It also explores the question of whether an education system that sorts pupils at a very early age is more cost-effective than a system that does not sort pupils during compulsory education. The stylised description of national education system is based on various sources of information. The data used in the cost analysis come from OECD and UNESCO. Due to data limitations, the analysis of system performance is based on student achievement only in mathematics and science. The data are drawn from the Third International Mathematics and Science Study (TIMSS) conducted in 1994-1995 by the International Association for the Evaluation of Educational Achievement (IEA).